Introduction

The semiconductor detectors technology has dramatically changed the broad field of X- and γ-rays spectroscopy and imaging. Semiconductor detectors, originally developed for particle physics applications, are now widely used for X/γ-rays spectroscopy and imaging in a large variety of fields, among which for example, X-ray fluorescence, γ-ray monitoring and localisation, non-invasive inspection and analysis, high energy astronomy, and diagnostic medicine. The success of semiconductor detectors is due to several unique characteristics as the excellent energy resolution, the high detection efficiency and the possibility of development of compact and highly segmented detection systems. Among the semiconductors device, silicon (Si) detectors are the key detectors in the soft X-ray band (<15 keV). Si-PIN diode detectors and silicon drift detectors (SDDs) [1], operated with moderate cooling by means of small Peltier cells, show excellent spectroscopic performance and good detection efficiency below 15 keV. On the other side germanium (Ge) detectors are unsurpassed for high resolution spectroscopy in the hard X-ray energy band (>15 keV) and will continue to be the first choice for laboratory-based high performance spectrometers [2].

However, in the last decades, there has been an increasing demand for the development of room temperature detectors with compact structure having the portability and convenience of a scintillator but with a significant improvement in energy resolution and/or spatial resolution. To fulfill these requirements, numerous high-Z and wide band gap compound semiconductors have been exploited [3,4]. In fact, as demonstrated by the impressive increase in the scientific literature and technological development around the world, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe or simply CZT) based device are today dominating the room temperature semiconductor applications scenario, being widely used for the development of X/γ-ray instrumentations [5,6].

In this paper we will focus on a particular type of detectors based on sensitive elements of CZT namely, spectrometers with spatial resolution in three dimensions. These, in fact, represent the new frontiers for applications in different fields that require increasing performance such as high energy astrophysics, the environmental radiation monitoring, medical diagnostics with PET and inspections for homeland security. The advantages offered by the possibility to reconstruct both the position of interaction of the incident photons in three dimensions (3D) and the energy deposited by each interaction are of fundamental importance for applications that require a high detection efficiency even at high energies (> 100 keV), i.e. in the Compton scattering regime, as well as a wide-field localization of the direction of incidence and a uniform spectroscopic response throughout the sensitive volume. In fact the possibility to reconstruct the photon interaction position in 3D will allow to correct from signal variations due charge trapping and material non uniformity and therefore allow to increase the sensitive volume of each detector unit without degrading the spectroscopic performance.

Principles of Operation

The typical operation of semiconductor detectors is based on collection of the charges, created by photon interactions, through the application of an external electric field. The choice of the proper semiconductor material for a radiation detector is mainly influenced by the energy range of interest. Among the various interaction mechanisms of X-rays and gamma rays with matter, three effects play an important role in radiation measurements: photoelectric absorption, Compton scattering and pair production. In photoelectric absorption the photon transfers all its energy to an atomic electron, while a photon interacting through Compton process transfers only a fraction of its energy to an outer electron, producing a hot electron and a degraded photon; in pair production a photon with energy above a threshold energy of 1.02 MeV interacts within the Coulomb field of the nucleus producing an electron and positron pair. Neglecting the escape of characteristic X-rays from the detector volume (the so called fluorescent lines), only the photoelectric effect results in the total absorption of the incident energy and thus gives useful information about the photon energy. The interaction cross sections are highly dependent on the atomic number. In photoelectric absorption it varies as Z^4,5, Z for Compton scattering and Z² for pair production.

Semiconductor detectors for X-ray and γ ray spectroscopy behaves as solid-state ionization chambers operated in pulse mode. The simplest configuration is a planar detector i.e. a slab of a semiconductor material with metal electrodes on the opposite faces of the semiconductor (Figure 1). Photon interactions produce electron-hole pairs in the semiconductor volume through the discussed interactions. The interaction is a two-step process where the electrons created in the photoelectric or Compton process lose their energy through electron-hole ionization. The most important feature of the photoelectric absorption is that the number of electron-hole pairs is proportional to the photon energy. If E is the incident photon energy, the number of electron-hole pairs N is equal to E/w, where w is the average pair creation energy. The generated charge cloud is Q₀ = eE/w. The electrons and holes move toward the opposite electrodes, anode and cathode for electrons and holes, respectively (Figure 1).

Figure 1. Planar configuration of a semiconductor detector: (a). Electron–hole pairs, generated by radiation, are swept towards the appropriate electrode by the electric field; (b) the time dependence of the induced charge for three different interaction sites in the detector (positions 1, 2 and 3). The fast rising part is due to the electron component, while the slower component is due to the holes

The movement of the electrons and holes, causes variation ΔQ of induced charge on the electrodes and it is possible to calculate the induced charge ΔQ by the Shockley–Ramo theorem [7]. The charge collection efficiency is a crucial property of a radiation detector and affects the spectroscopic performances and in particular the energy resolution. High charge collection efficiency ensures good energy resolution which also depends by the statistics of the charge generation and by the noise of the readout electronics. Therefore, the energy resolution (FWHM) of a radiation detector is mainly influenced by three contributes:

The first contribution is the Fano noise due to the statistics of the charge carrier generation. In semiconductors, the Fano factor F is much smaller than unity (0.06–0.14) [8]. The second contribute is the electronic noise which is generally measured directly using a precision pulser, while the third term takes into account the contribution of the charge collection process. Different semi-empirical relations have been proposed for the charge collection contribution evaluation of different detectors [9]. (Figure 2) shows a typical spectroscopic system based on a simple semiconductor detector. The detector signals are amplified by a charge sensitive preamplifier (CSP) and then shaped by a linear amplifier (shaping amplifier). Energy spectra are obtained by a multichannel analyzer (MCA) which samples and records the shaped signals.

Figure 2. Block diagram of a standard spectroscopic detection system for X- and γ-rays.

3D CZT Sensor Configurations and Developments

One of the most recent development in this field regards the so called three dimensional (3D) detectors. A 3D spectrometer is, in principle, a detector divided into volume elements (voxels), each operating as an independent spectroscopic sensor. The signal produced in each voxel by the interaction of an incoming X/γ photon must be able to be is read and converted into a voltage signal proportional to the energy released. If the readout electronics of the detection system implements a coincidence logic, it will be possible to determine to some extent the history of the incident photon inside the sensitive volume by associating the energy deposits in more voxels to the same incident photon. The need for this type of sensors comes from the applications requirements. For example, in the field of hard X- and soft γ-rays astrophysics (10–1000 keV), there are promising developments of new focusing optics operating for up to several hundreds of keV, through the use of broadband Laue lenses [10] and new generation of multilayer mirrors [11]. These systems make it possible to push the sensitivity of a new generation of innovative high energy space telescopes at levels far higher (100–1000 times) than current instrumentation. To obtain the maximum return from this type of optics up to MeV, then you it is required the use of focal plane detectors with high efficiency (> 80%) even at higher energies and with that shall have also the ability to measure the energy spectrum with good spectroscopic resolution and also to localize accurately (0.1–1 mm) the point of interaction of the photons used for the correct attribution of their direction of origin in the sky.

In fact the realization of 3D spectrometers by a mosaic of single CZT crystals is not as easy as for the case of bi-dimensional imagers, mainly because to the small dimension of each sensitive unit necessary to guarantee the required spatial resolution and also for the intrinsic difficulty of packaging in 3D sensor units in which each one requires an independent spectroscopic readout electronics chain. A solution is offered by the realization of stack of 2D spectroscopic imagers [12, 13]. This configuration, is very appealing for large area detector, but has several drawbacks for application requiring fine spatial resolution in three-dimension and compactness. Indeed the distance between each 2D layer of the stack limits the accuracy and the sampling of the third spatial coordinate as well as passive materials are normally required for mechanical support.

To solve this kind of problems, in the last 10–15 years, there have been several groups that have focused their activity on the development of sensors based on high volume (1–10 cm³) crystals of CZT/CdTe capable of intrinsically operating as 3D spectrometers and therefore able to meet the requirements for certain applications, or to make more efficient and easy the realization of 3D detectors based on matrices of these basic units. The main benefits are: a limited number of required readout channels to achieve the same spatial resolution, packing optimization and a reduction of passive material between sensitive volumes. In these developments, a key role is played by the adopted electrode configurations. Various electrode configurations have been proposed and studied to improve both the spectroscopic performance and the uniformity of the response of CZT detectors compensating and correcting problems related to trapping and low mobility of the charge carriers in these materials. In fact, these electrode configurations, with the implementation of appropriate logical reading of the signals, makes it intrinsically able to determine the position of interaction of the photon in the direction of the collected charge (depth sensing) and therefore are particularly suited to the realization of 3D monolithic spectrometers without requiring a drastic increase of the electronics readout chains. In the framework of a project recently funded by the Italian Space Agency we are working on the development of a 3D CZT prototype for astrophysical applications and, in particular, on the realization of an advanced front-end electronics based on the RENA3 ASIC suitable for a flexible qualification and characterization of several CZT crystal samples. Here we report some detail about the development of this electronics.

Electronic chain for selection and qualification of 3D CZT detectors

The processing of the signals provided by a 3D CZT detector required to obtain an imaging-spectroscopy device needs sophisticated electronics. The detector treated here, for example, is biased so as to provide the signals through three different types of electrodes: anodes, cathodes and drift strips. For this reason the front-end electronics has to be able to process signals of both polarities, positive and negative, in the case of cathodes and anodes, and of a polarity unknown in the case of the drift strip. The main function of the analogue front-end electronics (AFEE) is to connect the 12 anode strips and the 10 cathodes to a RENA-3 ASIC from NOVA R&D Inc. (CA, USA) used as signal readout device (RENA-3TM IC User Specifications Rev 1.31, May 11, 2015). The RENA-3 ASIC is a 36- channel charge sensitive amplifier self-triggering. Each channel includes a low-noise preamplifier, a shaper with sample/hold, and in addition a fast shaper that gives a trigger signal for coincident event detection. The signal range is selectable channel by channel over two full scales (equivalent to 200 keV and 1.3 MeV for CZT) as the peaking time that ranges from 0.1 to 40 μs. The comparator thresholds can be adjusted through an 8 bit DAC on each channel in order to obtain an accurate and uniform threshold setting. A pole-zero cancellation circuit is available for minimizing pileup errors. All these features are selectable by software and are independent for each input channel.

A very important feature for our purposes is the presence of two trigger chains, a “slow” and a “fast”, each of which has programmable thresholds, independent of each other and configurable channel by channel. Through the slow trigger chain and the associated digital register, it is possible to know which channels produced a trigger, or in other words which channels were affected by an event with energy higher than set threshold. This information allows to digitally convert only the triggered channels (sparse MODE), thus contributing to the decrease of the total acquisition time and then of the dead time. In any case, there is always the possibility to digitally convert all 36 channels, independently by the trigger condition and consequently increasing the system dead time. The slow trigger signal starts the acquisition phase sampling and holding, of the 10 cathodes and the 12 anodes signals. The acquired signals are then digitized by an external ADC, managed by an FPGA, which converts one channel at a time given the presence of a single output. Peak detector, present in each channel, allows to keep the maximum value of the signal for a necessary time to be able to convert all channels by the single external ADC. The fast trigger chain allows the time-stamp implementation within each individual channel and the generation of the system trigger. The time-stamp function is obtained through two cells that sample and hold the amplitude of two quadrature sinusoids when channel fast trigger occurs. The acquired sinusoids values are extracted and digitized using the same acquisition procedure. From the knowledge of these values it possible univocally determine to the timing informations within a period of the two sinusoids. Therefore, with this technique it is possible to establish the time interval between an event detected by two different portions of the detector belonging to two different channels of the RENA3.

Moreover, in our system the fast trigger is sent to an FPGA, in which it runs an algorithm with configurable parameters, that triggers the acquisition of the signal produced by the drift strips. The digitized data related to signal and time intervals are transferred from the FPGA to the PC, in which a software allows to calculate the energy collected by each electrode and relate it to the events recorded by the drift strips and taking into account temporal coincidences.

The block diagram of the system is shown in the figure:

Several analysis and characterization systems are being developed to study 3D-CZT detectors, that use fast ADCs and algorithms that run on FPGA, aimed at reducing the large amount of data produced by sampling. These systems have the advantage of providing to the user all the informations of each single event. On other hand the “firmware” algorithms, involved to reduce the big amount of data, are hard to optimize. Furthermore, fast components and high-performance algorithms running on FPGA, required more power than an acquisition system based on peak detector.

We are realizing a system that does not want to achieve performance of fast sampling or the processing of digital data in real-time, but wants to reach a good compromise between performance, space and power consumption requirement so that it can be well exploited in space applications.

Considerations on 3D CZT Spectrometers Applications

The development of CZT spectrometers with high 3D spatial resolution and fine spectroscopy represent a real challenge to the realization of a new class of high performance instruments able to fulfil the current e future requirements in several applications fields. The possibility to achieve also a very good detection efficiency, even at high energy (up to few MeV) [14], because of the sensitive volumes that can be obtained also by mosaic or stack of 3D sensor unit, without losing significantly their spectroscopic performance and response uniformity, together with their capability to operate at room temperature, are really appealing for application as radiation monitoring and identification [7] and homeland security as well as in industrial non-invasive controls and, in the research field, for new hard X- and soft γ-ray astronomy instrumentations. Furthermore, the fine spectroscopy (few % at 60 keV and <1% above 600 keV) and the high 3D spatial resolution (0.2–0.5 mm), that these devices can guarantee coupled with an high performance readout electronics, allow to operate not only in full energy mode, but also as Compton scattering or pair detectors if equipped with an appropriate electronics providing a suitable coincidence logic to handle multi hit events. This possibility imply that these sensors are suitable to realize wide field detector for γ-ray sources (> 100 keV) localization and detection both in ground and space applications [15]. Evaluation done using a single 3D CZT sensor, as a 4π Compton Imager, has demonstrated the possibility to obtain an angular resolution ~15° at 662 keV. This is really an excellent result in the small distance scale used to reconstruct the Compton events kinematics and can be achieved only because the good 3D and spectroscopic performance of the CZT proposed sensor units.

On the possibility to operate 3D spectrometers as Compton scattering detectors rely the appealing opportunity to utilize these devices for measurements of hard X- and soft γ-rays polarimetry. Today, this type of measurement is recognized of fundamental importance in high energy astrophysics and is one of the most demanding requirements for next space mission instrumentation in this energy range (10–1000 keV). The presence of linearly polarized photons in the incoming flux from a cosmic source determine a modulation in the azimuthal direction of Compton scattered events. A 3D spectrometer able to handle properly scattered events is intrinsically able to measure this modulation, i.e. operate as a scattering polarimeter [15]. The quality (modulation factor) of a scattering polarimeter is strictly dependent on his spatial resolution and spectroscopic performance. Several experimental measurements [16,17, 18] and simulation model have demonstrated that a detector allowing a good selection of events using both the spectroscopic and position information of each hits can achieve very high modulation factor. In particular the possibility to select events within thin layer of the sensitive volume, thanks to the intrinsic 3D segmentation of the detector (i.e. close to 90° scattering direction), drastically improve the modulation factor and therefore the reliability of the polarimetric measurements.

References

1. Lechner P (2004) Novel high-resolution silicon drift detectors. X Ray Spectrometry 33; Pg No: 256.
2. Eberth J, Simpson J (2006) From Ge (Li) detectors to gamma-ray tracking arrays-50 years of gamma spectroscopy with germanium detectors. Progress in Particle and Nucl Phys 60; Pg No: 283.
3. Owens A, Peacock A (2004) Compound semiconductor radiation detectors. Nucl Instr and Meth in Phys Res A  531; Pg No: 18.
4. Sellin PJ (2003) Recent advances in compound semiconductor radiation detectors. Nucl Instr and Meth in Phys Res A 513; Pg No: 332.
5. Lebrun F (2003) ISGRI: The INTEGRAL Soft Gamma-Ray Imager. Astronomy & Astrophysics 411; Pg No: L141.
6. Ogawa K, Muraishi M (2010) Feasibility Study on an Ultra-High-Resolution SPECT with CdTe Detectors. IEEE Trans. on Nucl. Sci 57; Pg No: 17.
7. Wahl CG, He Z (2011) Gamma-Ray Point-Source Detection in Unknown Background Using 3D-Position-Sensitive Semiconductor Detectors. IEEE Trans On Nucl Sci 58; Pg No: 605.
8. Devanathan R (2006) Signal variance in gamma-ray detectors – A review. Nucl Instr Meth in Phys Res A 565; Pg No: 637.
9. Kozorezov AG (2005) Resolution degradation of semiconductor detectors due to carrier trapping. Nucl Instr Meth in Phys Res A 546; Pg No: 207.
10. Frontera F (2013) Scientific prospects in soft gamma-ray astronomy enabled by the LAUE project. Proc of SPIE 8861, Pg No: 886106-1.
11. Della Monica Ferreira D (2013) Hard X-ray/soft gamma-ray telescope designs for future astrophysics missions. Proc. of SPIE 886; Pg No: 886116-1.
12. Watanabe S (2009) High Energy Resolution Hard X-Ray and Gamma-Ray Imagers Using CdTe Diode Devices. IEEE Trans on Nucl Sci 56; Pg No: 777.
13. Judson DS (2011) Compton imaging with the PorGamRays spectrometer. Nucl Instr and  Meth in Phys Res  652; Pg No: 587.
14. Boucher YA (2011) Measurements of Gamma Rays above 3 MeV using 3D Position-Sensitive 20×20×15 mm3 CdZnTe Detectors. IEEE Nucl. Sci Symp Conference Rec Pg No: 4540.
15. Xu D (2004) 4π Compton imaging with single 3D position sensitive CdZnTe detector. Proc of SPIE 5540; Pg No: 144.
16. Curado da Silva RM (2011) Polarimetry Study With a CdZnTe Focal Plane Detector. IEEE Trans On Nucl Sci 58; Pg No: 2118.
17. Antier S (2014) Hard X-ray polarimetry with Caliste, a high performance CdTe based imaging spectrometer. submitted to Experimental Astronomy.
18. Lee K (2010) Development of X-ray and Gamma-ray CZT detectors for Homeland Security Applications. Proc of SPIE 7664; Pg No: 766423-1.

Summary

A serious environmental problem, which affects most of the countries for years, is the massive use of tires, which once used, generate large stocks of waste material. A common method to process these used tires goes through crushing, in which the fiber, steel and rubber obtained from the crushing process are separated. This article affects the reuse of rubber obtained from these tires, also called GTR (Ground Tires Rubber), by mixing with various thermoplastic polymeric compounds, in order to improve some of its mechanical and structural properties, and at the same time, give exit to these surpluses that cause already used tires. For this purpose, the article analyzes the mechanical-structural properties of seven common thermoplastic polymers, which mixed with the GTR ) for a single particle size (p <200µm). could be useful in industrial processes. From the results obtained, it follows that this proposal is valid, in lower percentages of GTR (5% -10% of GTR) analyzed (from 5% to 70% of GTR).

Keywords

GTR, Recycling, Reuse, Composite, Microstructural Analysis, Mechanical Properties, Polymeric compounds, thermoplastics, Scanning Electronic Microscopy

Introduction

The environmental problem of the accumulation of used tires (GTR) [1–3] has driven the efforts of the scientific community to seek solutions for the recovery and reuse of these tires. In general, a thermoplastic or thermosetting polymer acts as a matrix and the elastomer (GTR) acts as a dispersed phase [4–6] or reinforcement. As in other two-phase polymer mixtures, in these compounds [7–8] the interfacial compatibility between components is basic to achieve the desired mechanical properties. In the case of recycled elastomers, the expected compatibility is low, so it is intended to increase this compatibility by reducing the degree of GTR crosslinking by devulcanization [9–11], also observing significant changes in the properties when we vary the particle size of GTR [12] reinforcement. The use of these recycled tires as reinforcements in composite materials has been extensively studied in numerous works of physical characterization of polymers with GTR particles, but in this case, a complete comparative mechanical and structural analysis of these properties in different compounds has been performed [13–15], quantifying how the presence of GTR in the polymer matrix modifies its mechanical behavior. The size of the GTR particles, in this work, is restricted to p <200μm. The aim is to analyze what percentage of GTR can be added to the different polymeric matrix polymers (PVC, EVA, HDPE, PP, PA, ABS and PS) analyzed, in order to keep their mechanical properties and structure of the polymers within acceptable values [16 -18]. For this purpose, several concentrations of Polymer / GTR (from 0% to 70% in GTR) have been analyzed, with one particle size, always with the GTR as a reinforcing agent. Some authors such as [19 -20] have observed that the presence of carbon black as reinforcement in composites increases the mechanical properties. Composite materials are heterogeneous, and their properties depend on the quantity, size and shape of the reinforcement, as well as other factors such as their preparation, or their compatibility.

[21] have studied different PVC samples with different compositions and varying proportions of additives such as carbon black (CB). Studies show that PVC with CB produces compounds that improve mechanical properties. In summary, the objectives of this research are to analyze and compare the mechanical-structural behavior of different composite materials obtained by mixing different polymers with different percentages of GTR (up to 70%) and, demonstrating that although the addition of GTR normally excludes industrial applications with high mechanical requirements, that pure polymers do provide, if they could, instead, be part of the recycling solution in many other industrial applications.

Materials And Methods

Materials

The following polymers have been used in this study: Polyvinyl Chloride (PVC); High density polyethylene (HDPE); The ethylene vinyl acetate (EVA) copolymer especially used for the production of extrusion films and coatings (18% vinyl acetate and 82% ethylene); Polypropylene (PP); Acrylonitrile butadiene styrene (ABS) white, consisting of 30% acrylonitrile, 20% butadiene and 50% styrene, being an amorphous thermoplastic material and highly impact resistant. Polyamide 6 (PA), known as Nylon 6, being a semi-crystalline thermoplastic that has high strength, toughness and impact resistance, showing good sliding behavior and good wear resistance; Polystyrene, (PS or styrene-butadiene-styrene), solid, transparent, hard and fragile, being an amorphous thermoplastic, highly resistant to impact. Regarding the GTR, with a particle size smaller than <200 μm, its content was verified by means of a TGA analysis, with 54% elastomers (36% natural rubber, and 18% styrene-butadiene), 29% of carbon black (CB) and 16% inorganic.

Preparation of the Compound

The recycled tire powders were dried in an oven at 100°C for 24 hours. Five samples of Polymer / GTR compound were prepared, varying the composition (5%, 10%, 20%, 40%, 50% and 70% GTR), for a single particle size (p <200μm). The mixing process was carried out with a Brabender mixing machine. Polymer / GTR laminates were obtained using a hot plate press at a constant pressure of 200 bar and different temperatures for 10 minutes, depending on the polymer to be treated. The samples for the test were prepared correctly in accordance with the specifications of Standard ASTM-D-638 type V. A sample of the pure polymer was also prepared with the same requirements for comparable results.

Microstructural Analysis

Scanning Electron Microscopy S.E.M. It was used to analyze the fracture surface of broken samples in stress-strain tests. It is possible to analyze the effects of this filler material on the matrix by observing the fracture surface of the polymer with the reinforcing particles. The images of the samples were analyzed according to the concentration of GTR. A JEOL 5610 microscope was used, and the samples were previously coated with a thin layer of gold in order to increase conductivity. The samples were photographed at 180 magnifications. The scanning electron microscope (MEB) is an instrument to obtain three-dimensional photographs because it has a high resolution and a great depth of field. In the photographs you can see the microstructure of microscopic samples. The SEM uses an electron beam instead of a light beam to form an image. It has a great depth of field, which allows a large part of the sample to be focused at the same time. In the scanning electron microscope, the sample is coated with a layer of carbon or a thin layer of a metal such as gold to give conductive properties to the sample.

Mechanical Analysis

The Tension-Deformation tests were performed with a Universal Instron 3366–10 kN machine, following the specifications of ASTM-D-638 Type V Standard. The test speed was 20 mm / min. The test temperature was 23 ± 2 ° C, and the relative humidity was 50 ± 5%. The study of mechanical properties, according to the concentration of GTR in the matrix and the size of the particles, includes the Modulus of Elasticity or Young’s, tensile strength, elongation at breakage and hardness or toughness. Five samples were used for each test.

Results And Discussion

Structural Analysis: Scanning electron microscopy, S.E.M.

SEM photomicrographs of the fracture surface of the Polymer / GTR specimens of the Deformation-Traction test [Section 2.4] are shown in Figure 2. It is observed that the GTR particles do not reach their melting temperature when mixing with the different polymers analyzed, so that they are observed in the microphotographs, GTR particles dispersed in the homogeneous medium (matrix of the different polymers), while the polymer reaches its melting temperature, its dispersion being correct. The result is a microgranulated mass with a degree of dispersion that depends on the mixing time and temperature, which does not facilitate cohesion between phases, as can be seen in the different analyzed micrographs. Figures 2-a; 2-f and 2-g, shows compounds with low concentration of GTR (10%). It is observed that the particle of the reinforcement is integrated and covered practically by the matrix, showing a good interfacial adhesion. There are no gaps in the contour of the particle, and polymer fragments are dispersed over the entire surface of the particle by adhering to it. Figures 2-b, 2-d, 2-h, on the contrary, show compounds with high concentrations of reinforcement (40% -70% GTR), which causes an increase in faults and cracks in the matrix, worsening interfacial adhesion. In this case, the percentage of thermoplastic polymer is not sufficient to wrap the GTR particles, so that the joint is more difficult, cracks and pores of considerable size appearing in its contour. The GTR particles are clean and easy to extract, so the fracture has occurred through the interface of the matrix. On the other hand, with high concentrations of GTR there are greater possibilities of particle agglomeration, this agglomerate acting as a large particle.

Table 1. Main processing characteristics of the different polymers used

Figure 1. Scanning electron microscopy S.E.M., used for the Structural analysis of Polymer / GTR compounds. a) Scanning Electron Microscopy JEOL 5610. b) electrolytic coating machine (sputtering). c) Sample holder of the S.E.M., with the samples coated in a layer of 20 nanometers of gold.

Figure 2. SEM photomicrographs of the Polymers – GTR, for some concentrations of GTR particles in the polymer: a) EVA / GTR-10%; b) HDPE / GTR-40%; c) PA / GTR-20%; d) PVC / GTR-40%; e) PP / GTR-20%; f) ABS / GTR-10%; g) PS / GTR-10%; h) PS / GTR-70%

Results of Comparison Of Mechanical Properties

Through the Tension-Deformation test, the mechanical properties of the different polymers with different concentrations of GTR and size of reinforcement particles (p <200μm) in the polymer matrix have been analyzed. Regarding Young’s Module (Figure 3. a)), we can see how the compounds of EVA, HDPE and PS have a better performance with the addition of low percentages of GTR (5–10%) in the compound. In the rest of materials, generally, from the addition of GTR particles, Young’s Module worsens. A very clear case is the EVA copolymer, which has lower Young’s modulus properties and improves with the incorporation of GTR. In tensile strength (Figure 3. b)), we can see more evident decreases for concentrations greater than 10% of GTR, except for HDPE compounds, which exhibit better behaviors with the addition of quantities of GTR in low proportions (5–10% of GTR).

Regarding the elongation at break of the GTR compounds (Fig. 3. c)), the highest level is for the EVA compounds, which range between 700% and 350%, for 0% GTR concentrations. to 20% respectively. The reduction of the deformability of the elastomer influences the decrease in elongation and, subsequently, the decrease in hardness, showing similar behaviors in terms of hardness for compounds with EVA / GTR. The decrease in elongation at break is related to imperfect interfacial adhesion between the components, as discussed previously in section 3.1. The incidence of poor adhesion between phases is a particularly important result. Elongation at break with the addition of GTR particles decreases dramatically, rising only in the case of PA, with the addition of GTR. Regarding the tenacity (Figure 3. d)), these falls are even greater. The toughness ranges decrease for concentrations of 10% GTR. From the observation of the comparative graphs of tenacity (J) it can be seen that, the ones with the greatest energy to produce the fracture are EVA and PP. For EVA or PP that add 10–20% GTR, the breakage energies of the compound decrease significantly. For PP, ABS and, to a lesser extent, HDPE, the addition of GTR negatively affects the properties of tear strength (J). A very prominent case is the PVC and PA polymers, which show very low breaking energy values for the pure polymer and improve this property (strength) with the addition of the percentage of GTR in the polymer matrix.

Figure 3. a) Young’s modulus (MPa), b) Tensile strength (MPa), c) Elongation at break (%), d) Tenacity or hardness (J), for the seven Polymer / GTR concentrations and particle sizes p <200μm.

A deeply Comparative-Analysis Stress-Strain model is needed, for a further research we can obtain curves obtained from the test of the polymers mixed with the full range of GTR concentrations. In this case, the complex morphology of the matrix polymer blended with GTR particles does not allow the use of the standard elastoplastic equations or the classical approach. For this reason, and in the same way as purposed [22], a simple uniaxial tensile stress–strain relation is proposed, based on three parameters, σ_Y, ε_Y, and n, where σ_Y is the yield strength and ε_Y the elongation at yield.

[1]

Conclusions

There are necessary for a deep analysis of the compounds analyzed, through DSC, Differential Scanning Calorimetry, that allows the study of those processes in which enthalpic variation occurs, for example determination of specific calories, boiling points and fusion, purity of crystalline compounds, reaction enthalpy and determination of other first and second order transitions. The calorimetry applied to the composite materials is used as a tool to detect the possible changes in the crystallinity and microstructure of the matrix by adding a second component as a reinforcement [23–24]. By measuring the melting temperatures and enthalpy of the compounds, these changes can be analyzed through DSC analysis. The thermal behavior of the compounds can be studied using DSC, the final thermogram (heat / temperature flow) is obtained. The melting point of the sample and the glass transition temperature can be obtained to determine the modification of the internal structure of the matrix and possible reactions that may occur in the mixture. So, in this sense can be an interesting analysis for further research.

Comparatively, it can be deduced from the observation of the results of HDPE, PVC, EVA, PP, PA, ABS and PS with GTR, that the analyzed mechanical properties of the compounds may have some significant changes depending on the amount of GTR that is supplied to the polymer matrix, that is, some properties vary according to the percentage of GTR added. As can be seen in section 3.2, generally the highest property values correspond to the pure polymer (0% GTR). Thus, for EVA, HDPE, PA and PS, some mechanical properties are improved by the addition of microparticles (p <200 µm) of GTR in the polymer matrix. With low concentrations of GTR (5–10%), the Young’s Modulus of the compound increases, although other mechanical properties decrease as with the compounds of EVA, PS and HDPE. This behavior may be due to the fact that the reinforcement matrix is correct for these formulations (as shown in section 3.1 of this investigation) and, therefore, some mechanical properties improve. However, for GTR concentrations greater than 10%, all mechanical properties decrease, except for PA compounds. The results obtained from the analysis of these compounds show the limit concentration of GTR in order to maintain acceptable values of the mechanical properties is of the order of 5–10% in general, values that would allow its use in various fields of industry with mechanical solicitations not too high, giving out disused amounts of GTR, as other authors have studied before, GTR compounds can be reused with other applications [25–26]. At a structural level we see a clear relationship between structural properties and mechanical properties, relating the compounds that show better internal cohesion (Section 3.1), compounds with low proportions of GTR (10%) and that coincide with the compounds that have better mechanical properties. Likewise, with high concentrations of GTR (from 40% to 70% GTR), we see how the mechanical-structural properties progressively worsen with the addition of percentages of GTR, as the photomicrographs performed at 180 magnifications with electron microscopy show. What clearly reveals the structural study is that the interaction between the polymeric matrix with the GTR particles is very weak and low

Financing: This research was funded by the MINISTRY OF ECONOMY AND COMPETITIVENESS, Government of Spain ENE2015-64117-C5-3-R (MINECO / FEDER).

Conflicts of Interest: The authors declare no conflict of interest.

References

1. European Tyre Recycling Association (ETRA). www.etra-eu.org (accessed aug 14, 2018)
2. Used Tyre Working Group (UTWG). Tyre Recycling; Department of Trade and Industry: London, UK. www.tyredisposal.co.uk (accessed novembrer 18, 2006).
3. Liu HS, Richard CP, Mead JL and Stacer RG. Development of Novel Applications for Using Recycled Rubber in Thermoplastics. Technical Research Program. Chelsea Center for Recycling and Economic Development, University of Massachusetts: Lowell, 2000.
4. Figovslq O, Beilin D, Blank N, Potapo J and Chernyshe V. Development of polymer concrete with polybutadiene matrix. Cem Concr Compos. 1996, 18, 437–444.
5. Hernandez-Olivares F, Barluenga G, Bollatib M and Witoszekc B. Static and dynamic behaviour of recycled tyre rubber-filled concrete. Cem Concr Compos. 2002, 32, 1587–96.
6. Goncharuk GP, Knunyants MI, Kryuchkov AN and Obolonkova ES. Effect of the specific surface area and the shape of rubber crumb on the mechanical properties of rubber-filled plastics. J Polym Sci Part B: Polym Chem. 1998, 40, 166–169.
7. Dierkes WK. Rubber recycling. In Recent research developments in macromolecules, Pandalai SG, Ed.; Trivandrum: Research Signpost, 7, 265–292, 2003.
8. Radeshkumar C and Karger-Kocsis J. Thermoplastic dynamic vulcanisates containing LDPE, rubber, and thermochemically reclaimed ground tyre rubber. Plast Rubber Compos. 2002, 31, 99–105.
9. Yehia A, Mull MA, Ismail MN, Hefny YA and Abdel-Bary EM. Effect of chemically modified waste rubber powder as a filler in natural rubber vulcanizates. J Appl Polym Sci. 2004, 93, 30–36.
10. Colom X, Andreu-Mateu F, Cañavate FJ, Mujal R and Carrillo F. Study of the influence of IPPD on thermo-oxidation process of elastomeric hose. J Appli Polym Sci. 2009, 114, 4, 2011–2018.
11. Cepeda-Jimenez CM, Pastor-Blas MM, Ferrándiz-Gómez TP and Martín-Martinez JM. Surface Characterization of vulcanized Rubber treated with sulphuric acid and its adhesion to polyurethane adhesive. J Adhesion. 2000, 73, 135–160.
12. Mujal R, Marín-Genescà M, Orrit J, Rahhali A, Colom X, Dielectric, mechanical, and thermal characterization of high-density polyethylene composites with ground tire rubber. Journal of thermoplastic composite materials. 2012, 25, 5, 537–559
13. Mujal, R.; Orrit J., Ramis, X.; Marin-Genesca, M.; Rahhali, A. Study on dielectric, mechanical and thermal properties of polypropylene (PP) composites with ground tyre rubber (GTR). Polymers & Polymer Composites (ISI). 2012, 20, 9.
14. Mujal, R.; Ramis, X.; Orrit-Prat, J; Marin, M. Study on dielectric, thermal, and mechanical properties of the ethylene vinyl acetate reinforced with ground tire rubber. Journal of Reinforced Plastics and Composites0. 2011, 30, 7, 581–592
15. Mujal R, Orrit-Prat J, Ramis-Juan X, Marin-Genesca M. Electrical application of polyamide reinforced with old tire rubber (ground tire rubber): Dielectric, thermal, mechanical and structural properties. Journal of thermoplastic composite materials. 2014. 27, 9, 1209–1231
16. Nakason C, Kaesaman A and Supasanthitikul P. The grafting of maleic anhydride onto natural rubber. Polym Test. 2004, 23, 35–41.
17. La Mantia FP, Lo Verso S and Tzankova Dintcheva N. EVA Copolymer Based Nanocomposites. Macro Mat Eng. 2002, 287, 12, 909–914.
18. Kim JI, Ryu SH and Chang YW. Mechanical and dynamic mechanical properties of waste rubber powder/HDPE composite. J Appl Polym Science.  2000, 77, 2595–2602.
19. Markov A., Fiedler B., Schulte K. Electrical conductivity of carbon black/fibres filled glass-fibre-reinforced thermoplastic composites. Composites Part A: Applied Science and Manufacturing. 2006, 37, 9, 1390–1395
20. J.R. Pothnis , M. Sridevi, M.K. Supreeth , A.R. Anilchandra, G. Hegde, S. Gururaja. Enhanced tensile properties of novel bio-waste synthesized carbon particle reinforced composites. Materials Letters 251 (2019) 110–113.
21. Saad ALG, Aziz HA and Dimitry OIH. Studies of Electrical and Mechanical Properties of Polyvinyl chloride) Mixed with Electrically Conductive Additives. J Appl Polym Science. 2004, 91, 1590–1598.
22. Giroud, J.P. Mathematical model of geomembrane stress-strain curves with a yield peak. J. Geotext. Geomembr. 1994, 13, 1–22.
23. N. Aini Fauziyah , A. Rosyidy Hilmi, M. Zainuri, M. Zainul Asrori, M.i Mashuri, M. Jawaid, S. Pratapa. Thermal and dynamic mechanical properties of polyethylene glycol/quartz composites for phase change materials. J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.48130
24. A. A. Gadgeel , Shashank Tejrao Mhaske. Novel approach for the preparation of a compatibilized blend of nylon 11 and polypropylene with polyhydroxybutyrate: Mechanical, thermal, and barrier properties. J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.48152
25. Colom X., Cañavate J., Carrillo F. Structural and mechanical studies on modified reused tyres composites. Eur Polym Journal. 2006. 42. 2369–2378.
26. Kim JI, Ryu SH and Chang YW. Mechanical and Dynamic Mechanical Properties of Waste Rubber Powder/HDPE Composite. J. Appl. Polym. Science. 2000, 77, 2595–2602.

Abstract

The application of nano materials, in developing a novel class of fiberoptic modulators, is presented. The developed modulators are capable of high speed modulation up to 140 Gbps. The technology is based on building the device directly on the surface of the optical fiber core in a cylindrical symmetrical and uniform fashion, for polarization independent and ultra high speed applications. The design of the device is based on modifying optical fibers by removing the fiber jacket and the passive cladding materials off a very short length of the fiber. Then, the fiber core, in the modified section, is coated with a multilayer structure of nano-materials. This modified cladding includes a nano layer of high-speed electro-optic polymer sandwiched between two nano metallic electrodes, for modulating signals application. In this way, the device speed can reach up to 140Gbps and more, based on the polymer’s improved electro-optic properties. Also, this structure can eliminates polarization dependent problems associated with all available integrated rectangular waveguide modulators. Which are used in most optical telecomm networks. Demonstration prototypes have been manufactured and successfully tested, and the proof of concept is completed.

OCIS Codes: Fiberoptic, Nano-materials, Optical modulators/switches, Optical communication, Optical networks, EO polymer, EO devices, Optical active devices, On-fiber devices.

http://www.photonicslabs.com;
http://www.photonicsonfiber.com;
https://www.linkedin.com/pub/dr-mahmoud-el-sherif/7/ab6/38b

Introduction

Because of the importance of integrated optics in optical communication networks, a great deal of effort has been expanded to take the advantage of newly developed nano materials to build Electro Optic (EO) devices directly onto the core of regular optical fibers, wherein, optical fibers can be used as active devices as well as the optical transmission link. In this way, many of existing problems associated with integrated optics can be eliminated, such as insertion loss associated with coupling optical signals between integrated optical devices and communication networks.

In this Letter, an overview on development of a novel class of fiberoptic modulators is presented. The development is based on using advances in nano materials in manufacturing active devices directly on the fiber core, in a symmetrical cylindrical and uniform structure. Also, this design eliminates polarization dependent in existing devices, which are constructed of rectangular waveguides acting as the device active channel. This technology can be applied to any ordinary optical fiber. So, the fiber can be used as an active device as well as the communication link, in any fiber network.

Most commercially available EO modulators are constructed of rectangular waveguides, made of Lithium Niobate (LiNbO₃) crystals. They are polarization dependent devices. Therefore, the device has to be positioned next to the light source, or a polarization maintaining fiber has to be used between the light source and the device. Therefore, using this type of devices in any fiber network, imposes certain limitations on the device location with respect to the light source. Also, coupling light between the active channel of the device, which is a rectangular waveguide, and the circular cross section of the fiber core is another challenge.

In this Letter, a brief explanation of the developed technology is presented. The technology has been successfully tested in development of an EO modulator, and proof of concept has been completed. A demonstration prototypes have been manufactured and tested at low frequency. Results show perfect match between the modulating electric signals and the modulated optical signals, even when a triangle modulating signal was applied. The manufacturing of the devices is based on using novel processing techniques to have full control on the deposition thickness uniformity and parameters for each layers of the applied nano materials.

Available Technology

For more than three decades, much effort has been directed to the development of high-speed EO modulators for optical communication networks, using LiNbO₃ rectangular waveguide as the device active channel [1,2]. The effort focused on improving the modulation efficiency as well as reducing insertion loss associated with those integrated devices. However, those modulators are polarization dependent, very costly and still have shown other drawbacks including coupling mismatch, and high insertion loss, when connected to fiberoptic networks.

On the other hand, the development of the high-speed EO polymers has resulted in a new generation of integrated EO modulators. The EO polymer is used as the active waveguide, to replace the single crystal LiNbO₃ modulators. A lot of research has been done to improve the properties of the developed EO polymers as well as modulation efficiency [3–6]. However, because of the rectangular shape of the active channel, polarization dependent is still a problem. The rectangular structure of the active channel of this type of modulators has imposed so many limitations and disadvantages. The modulator has to be positioned next to the light source output, to limit the effect of polarization dependent. However, experimental research has proven that; even when the modulator is positioned near to the light source, the polarization dependent is still a problem. This is clear from the test results reported in reference [3], when the modulating signal is a triangle wave. It is shown that the modulated signal cannot follow the shape of the modulating signal. Instead of having a single peak as in the modulating triangle signal, a double peak is shown in the modulated signal, as shown in Figure 4 [3].

Based on polarization problems associated with integrated rectangular waveguide modulators, there were several reported trials with the intention of building passive and active devices directly on the fiber core. Passive devices were mainly built for various sensors applications. One of the main advantages, of using on-fiber structure for sensors applications, is to improve signal stability and accuracy, because of the device polarization independent [7].

For active on-fiber devices, challenges were not easy for coating very thin multilayers nano materials onto the cylindrical surface of the fiber core. Early trials were reported in 1980’s, before electro-optic polymers were developed or known. Also, it was impossible to grow or deposit electro-optic crystals, such as LiNbO₃ crystal, on the cylindrical surface of the fiber core. Therefore, liquid crystals were used as the modified EO cladding [8, 9]. As a result, the problems of using rectangular waveguide were illuminated, however, using liquid crystal imposed sever limitation on the speed of the modulator.

Newly Developed Technology

Along with interest in solving the problems associated with those devices, a novel technology based on nano materials application, has been developed for manufacturing on-fiber modulators, as shown in Figure.1. This developed technology has resulted in a new class of polarization independent modulators. It is based on constructing a layer of nano EO material, as an active channel, sandwiched between two nano metallic electrodes directly on the cylindrical surface of the fiber core, in a cylindrical uniform structure. In his way, polarization dependent as well as coupling problems, exist between integrated devices and fiber networks, can be completely eliminated. This can be achieved by modifying a small section of ordinary optical fiber, replacing the passive cladding with an active multilayer cladding, using nano processing techniques. The multilayer modified cladding has to be surrounding the fiber core in a symmetric uniform 360^o cylindrical shape. Also, in this way, there will be no need to cut the optical fiber to integrate optical modulators into the fiber network. The advantages of using this novel structure are unlimited, ranging from simplicity and cost effectiveness to high efficiency and high signal to noise ratio, as well as the devices are all polarization independent, because of the symmetrical uniform cylindrical structure.

Figure 1.    A schematic of an on-fiber EO Modulator, wherein, the device is constructed directly on the cylindrical surface of the fiber core.

Design and Manufacturing

In this Letter, an overview of the design, manufacturing and testing of the on-fiber EO modulator is presented. The design is based on modifying ordinary optical fibers in a small section, to act as an EO modulator. The fiber jacket is removed by mechanical stripping, then, the passive cladding material is partially (or totally) etched away, by a standard chemical etching technique. The etching process rate has to be calibrated, then, applied under continuous light transmission, for full control on the final thickness. This modified section is then prepared for multilayer coatings by applying the proper mask, before each layer of coating, based on the required geometry of this coating layer, as shown in Figure. 2 for the first layer of coating. The coating process is performed for each layer of the multi-layer structure, in 360^o, as shown in Figure. 3.  After each coating step the mask is removed and a new mask is applied based on the geometry of the next coating layer. The modified cladding includes a number of nano-layer of different materials. One of the layers is a high speed EO polymer, sensitive to electromagnetic fields. The polymer is coated by a spinning technique, used under certain conditions for nano layer coating. This layer of EO polymer is sandwiched between two cylindrical coated nano metallic electrodes, using enhanced plasma deposition technique. The inner electrode is deposited first, then, the polymer layer is coated, wherein, the poling process of the polymer is achieved in-situ using the first deposited electrode, under high voltage application in a high temperature oven. This process is applied for a certain time, under vacuum and nitrogen gas, to generate the electro-optic property within the coated polymer. Then, the second nano-metallic electrode is deposited on the top of the EO polymer. Before and after each of the coating steps a special surface treatment is performed. After the last layer of nano-materials is coated, the jacket material is applied on the top of the second electrode, as shown in Figure. 4.

Figure 2.   A schematic of the modified section of the optical fiber, after stripping the jacket and etching the cladding, and with the mask ready for the first coating process.

Figure 3.   A schematic of the modified section of the optical fiber, after the multi-nano-layers coating, including the EO polymer and the two metallic electrodes.

Figure 4.   A schematic of the on-fiber EO modulator, after applying the jacket to the modified section, for handling and protection.

Several on-fiber EO modulators were manufactured and tested, based on the structural design explained before. For each modulator, after the passive cladding was etched away, the inner electrode was coated, in 360^o, on the top of the fiber core, using a transparent nano metallic material, using an enhanced plasma deposition technique modified for cylindrical coating of fibers. Then, the polymer base material was spin coated on the top of the inner electrode, while it was synthesized. Adjusting the spin coating process, speed and time, controls the thickness of the coated thin layer of the polymer. After drying in a nitrogen oven at room temperature, the polymer was radially poled for about one hour at the required temperature and voltage, using the corona poling method. It was then cooled down to the room temperature while keeping the poling voltage on. The thermosetting cross-link of the material system occurred simultaneously during the poling process. This process is very critical to satisfy the required change in the polymer high speed electro-optic property. Detailed information concerning the synthesis process and the in-situ poling of the polymer are reported elsewhere [5].

After the coating process of the EO polymer is completed, the outer metallic electrode was coated on the top of the EO polymer. Before coating any of the electrodes or the EO polymer, special chemical surface treatment was conducted to enhance interface properties. Then, the jacket material was applied on the top of the second electrode. The design of the jacket includes two exposed metallic rings, which are connected to the electrodes. All coated layers were designed in a symmetrically uniform cylindrical structure, in 360^o. The schematic of the manufactured EO modulator is shown in Figure. 4.

In the presence of a modulating signal, applied to the electrodes, an electromagnetic field is generated between the two electrodes resulting in changing the optical properties of the EO polymer, mainly the equivalent refractive index of the polymer material. This change will be uniform across the 360^o of the cylindrical surface of the fiber core, resulting in a uniform modulation of optical signals propagating within the fiber core, regardless of the polarization direction of the propagating optical signals within the fiber core. Thus, the problem of polarization dependent, in commercially available devices, has been eliminated. Another major advantage is that; modulation can exist at more than one location along the length of the same optical fiber, and can be far from the light source location.

Several modulators were manufactured and successfully tested. Different types of modulating signals (sinusoidal, triangle, and digital) were used for testing the manufactured devices. Also, two different experimental test set-ups (Mach zehnder or Michelson interferometers) were used in testing and proof of concept. All test results were encouraging, and modulated signals were always identical to the modulating signals. One of testing results, of the manufactured devices, is presented next.

Testing Results

Before testing the selected device, a reasonable packaging process was done, using available tools and facilities. An actual image of the packaged device is shown in Figure. 5, which is in size about 1.0in x 2.0in x 0.3in. Using the proper packaging tools and facilities, the device size can be reduced by 80% or more, and it can also be in a cylindrical shape with a diameter less than 0.3in and length about 1.0in to 1.5in. The packaging process includes the integration of a RF/MW socket connected from inside with the two electrode rings. Also, for fiber mechanical protection, two rubber sleeves were used to cover the exposed fiber ends.

Figure 5.    An actual image of the manufactured EO modulator, after packaging with a metallic shield box. The fiber two ends are exposed from both sides, and protected by two black rapper holder. The microwave socket is connect from inside with the two metallic rings on the fiber jacket, for direct application of the modulating signals.

A sample of the device test results is presented here, using the Michelson interferometer set-up. The schematic diagram of the Michelson test set-up is shown in Figure 6. The Figure shows two input signals to the oscilloscope. The inputs are the modulating electric signal and the photo-detector output, which is the modulated signal.

Figure 6.   A schematic of a Michelson interferometer test set-up, used for the evaluation and proof of concept of the developed on-fiber EO modulator, showing the input signal (as modulating electric signal) and the photo-detector output (as the modulated signal).

A sample of the test result is shown in Figure. 7. It shows that the modulating signal is a triangle signal. This type of modulating signal was selected to proof the high quality polarization independent. It is clear from Figure. 7 that the modulated signal is following exactly the shape of modulating signal, with a triangle shape too. For better understanding of the achieved high quality performance of this on-fiber modulator, a comparison has to be done with respect to the modulated signal of a device consisting of a rectangular waveguide channel. This was explained before, using the results reported in reference [3], which explain that when a triangle’ modulating signal is applied to a rectangular waveguide modulator, a double peak signal will result at the device output, as a result of the device polarization dependent. This polarization dependent is clear, as presented in reference [3], even when the device is positioned next to the light source as in Figure. 4 of the reference [3]. On the other hand, this novel on-fiber modulator shows a smooth single peak in the modulated signal, even when the device is positioned far from the light source. Therefore, the polarization dependent has been completely eliminated. Based on recent advances in available EO polymers the device speed can now reach 140 Gpbs, and expecting much higher speed in the near future. Also, the developed technology can be applied to other type of devices, such as EO switch, tunable couplers and wave division multiplexers.

Figure 7.   A sample of the test result showing a sawtooth (triangle) applied modulating signal and the photo-detector output of the modulated optical signal, using the Michelson interferometer setup in figure 6.

Conclusion

A novel class of on-fiber EO modulators has been developed, manufactured, and successfully tested, using advances in processing of nano-materials. The technology is based on building the device directly on the fiber core, after removing the fiber jacket and etching the cladding layer. For demonstration, an on-fiber modulator was manufactured, using a nano-layer of advance EO polymer as the active channel within the fiber modified cladding. The layer of the EO polymer was sandwiched between two uniform cylindrical electrodes. Ordinary optical fiber can be used for such application. The test results were encouraging and provide a clear proves on polarization independent. The device can be used for application up to 140Gbps, and can be constructed at any location on the optical fiber and fare from the light source. Multiple devices can also be constructed on the same fiber at different locations. The developed on-fiber technology can be used for the actual realization of all-fiber networks, where the fiber is used as an active device as well as the networking link. In addition, the technology has been tested in application to on-fiber switches, tunable couplers and tunable DWDM.

The author gratefully acknowledges that the EO polymer used in most developed and tested modulators were provided by Prof. Alex Jen and his group, including Dr. Antao Chen, and Dr. Jingdong Luo, of the University Of Washington, USA.

References

1. Ed L. Wooten, Karl M. Kissa, Alfredo Yi-Yan, Edmond J. Murphy, Donald A. Lafaw, et al. (2000) A Review of Lithium Niobate Modulators for Fiber-Optic Communications Systems. IEEE J. of Selected Topics in Quantum Electronics 6: 69–82.
2. High-Speed Photonic Devices, Edited by Nadir Dagli, CRC Press, Taylor & Francis Group, 2007
3. Dechang An, Zan Shi, Lin Sun, John M. Taboada, Qingjun Zhou, et al. (2000) Polymeric electro-optic modulator based on 1Ã2 Y-fed directional coupler. Appl. Phys. Lett  76: 1972–1974.
4. Dechang An, Suning Tang, Zu Zhou Yue, John Taboada, Lin Sun, et al. (1999) Linearized Y-coupler Modulator Based on Domain-inverted Polymeric Waveguide. SPIE Conference on Optoelectronic Interconnects VI, San Jose, California, SPIE, 3632: 220–231.
5. Ma H, Jen AK-Y, Dalton LR (2002) Polymer-based optical waveguides: Materials, processing, and devices Advanced Materials 14: 1339–1365.
6. Taylor EW, Nichter JE, Nash FD, F. Haas, Szep AA, et al. (2005) Radiation resistance of electro-optic polymer-based modulators Appl. Phys. Lett 86: 201122-1–201122-3.
7. Optical Guided-wave Chemical and Biosensors II, Chapter 5: Fiber Optic Chemical and Biosensors, Mahmoud El-Sherif, Editors M. Zourob and A. Lakhtakia, Springer-Verlag GmbH, Germany (2010)
8. El-Sherif MA, Shankar PM, Herczfeld PR, Bobb L, Krumboltz H (1986) On-Fiber Electro-optic Modulator/Switch. Appl. Opt 25: 2469–2470.
9. El-Sherif MA, Shankar PM, Herczfeld PR, Bobb L, Krumboltz H (1987) An on-fiber active transducer in Technical Digest, IEEE Fourth International Conference on Solid-State Sensors and Actuators,  200–203.

Abstract

New field theories considering new re-interpretations of field observables are used in a wider context to be applied in the design and development of energy technologies to fine different applications through the spectra of field observables and the particles interaction that act in the shedding, correction, alignment, cure, re-directing of the fields to different process. In it are of our interest those applications to Nano medicine and design of biomedical devices at quantum level. Also are mentioned some parallel developments realized in this respect.

Introduction

New Theories, New Re-interpretations of the Knowledge and New Tools to the Next One Hundred Years

New postulates and principles have been considered as given in [1,2] where the torsion field theory has been embraced by some as the scientific explanation of homeopathy [1,3], electromagnetic propulsion, magnetic levitation [2], and deep studies of the development and evolution of the Cosmos or space-time [4–6]. All before phenomena are related beyond the terrestrial technology and are connected under the same topological field theory and principles considering the same field theory developed through algebraic geometry and mathematical physics. In this respect, are used frequently the cohomological spaces as of the type H¹ (B, O(–k)), to explain and demonstrate the correspondences between helicities of the “quantum” fields bundles and the spin actions in spin manifolds developed. Last mentioned may be to the twistors (mini-twistors, ambitwistors and etcetera) in the correction and restoring of fields, or the introduction of the intention to transform a space, matter, body, organism or ambient of the any type [7].

The twistor geometry created Penrose [8], has been useful to describe from a point of view of the sources (that are singularities in usual differential geometry), the possibility to use the geometry created from start of these singularities. This last re-interpretation has been developed and also used in diverse research by me. However, has been necessary add some new concepts realising research in derived categories to explain the equivalences and different dualities that arise in this study.  In this new context, also arise the identification problem of the different topological groups or Lie groups that define the symmetries and other gauging actions in the interaction with the elements that offers the Universe. Recently, was realised a research on the field observable study and the duality of invariants in the Universe field equations through twistor-spinor framework in spectral theory of curvature to detection of gravitational waves [9].

In the last theme relative to the deep studies of the Universe, I have given several results that incorporate the fundamental principles of the matter in gravitation and a new re-interpretation of field observable under co-cycles defined in vector topological spaces [10–12]. However, these results go beyond treat to give a precise description of how functions the Universe from their Higgs boson [11].  Also are searched and wanted technologies, which derive of certain theorems to develop sensors and transducers of the field observable, having as final goal the creation of an advanced sensor of quantum gravity (see the figures 1 A), B), C) and D)) [13].

Also are of interest the quantum communication (telepathy, telekinesis, [15]) and the levitation (for example, this understood as the production of electro-antigravity described in the papers [5, 16, 17]. Here again we have used a cohomological space seemed to before, considering twistor geometry to describe the action of a rotation ring and their magnetic field in the movement of the ship in magnetic levitation).

In the mind phenomena as the clairvoyance and extra-sensorial perception [15], and other paranormal phenomena are had the same principles established to define field conscience by operators [18] in an integral operators theory that join the quantum mechanics with the relativistic and macroscopic theories of the Universe. Here under these arguments, are demonstrated that the second theories (relativistic and macroscopic theories) in reality are consequences of the quantum theories. Disorders in the mind are quantum perturbation generating coercive charges given energy weight that provoke the appearing of symptoms in the mind (see figure 2).

A). Curvature in microscopic level to analyse microcrystal deforming. B). Distribution of Neutrinos in the Universe [12, 14].
Figure 1. Field Detections through dilatons or gauge fields in the space-time and their relation with the SWAP mapping. Detection of the super-massive object (singularity) through sensor device to detect and measure quantum gravity using the fermionic spectral behaviour. Could be that the Universe field is the master control on our mind? If this is true then a good managing of photons as bosons of certain class could be the solution to all mental illness.

Figure 2. A). How begins the anxiety and their disorders? B). ……..what happens with the symptom space?

The application of torsion fields in medicine has been determining. Everything cure can be possible from photonics cure devices (including devices that cure all sickness such and as my hypothesis [1, 3] given to explain the appearing of organic illness and the re-composition of the fields by codes given by path integrals (Bulnes-Feynman integrals [1] to obtain the health).

Remember that one of my postulates and principles in the formal engineering theory is that the engineering is the creation of technology on the energy. Because, all is energy and as has been planted and demonstrated in a work [13], the Universe is all of energy because the unispace or universal covering is all of energy. The realised argumentations were done the global analysis that uses the universal covering of a Lie group with the causality (or causal structure).

This study consider the causal structure of the scattering phenomena through past and future light cones,  create the possibility of energy for one thousand years, perpetual motion  machines and star-gates (worm holes in the space) with advanced analogues as the synchrotronic propulsion (advanced spaceships)  and disintegrative mass weapons, using the same principles in all case.

Torsion fields can interact with laser beams (change frequency); creating effects of diverse, for example, in the biological processes, where torsion affects directly the ADN. Also can melting or solidifying some materials, affect quartz crystals increasing their properties as resonators. Also, affect some electronic components creating radiation coverings. The torsion can favourably change some beverages, and have been noted to affects gravity.

Spintronics and Micro-electronics Research

New theoretical developments have been given in quantum field theory^[1], more specific in micro-electronics, realizing research on advanced electronics, photonics and spintronics^[2], in the problems of electromagnetic propulsion, nano-medicine, sensors of field observables and transducers. Here is necessary to detach the importance of the obtained results in these research lines in electronics where have been complete theories with prototypes to detection of quantum gravity, cure of all illness, storage of energy through curvature and torsion energies, concept created [19, 20] to can to build the devices with technology on particles, fields, radiation and waves. Likewise, can be affirmed that the prospective in the use of the energy process of the electrons managing will give major developments of the advanced electronics considering no only their photon but also the use of their spin giving as result the spintronics [21]. This last also consider to the electron as the fundamental particle in all the processes of transference and information to the managing of other particles considering basal and transitory states of the electron through technologies, as are the dots, magnetons or spin-transistors.

Based and supported by important contributions and theorems on the deep study of the Universe, much of this research has been realized. Then have been given results in algebraic geometry and mathematical physics and published in the British and American journals of mathematics: Theoretical Mathematics and Applications [26], and other mathematics research journals [27].

Field Theory Applications in Nanomedicine

However, the vision of the research in field theory goes beyond the matter and molecular level. As has been mentioned in biomedical research scenarios [28], any illness begins in the atomic level through a collateral atomic damage when voracious protons are eating unstable electrons whose electronically information through photons is erroneous, and provokes the exit of these electrons attracted for voracious protons outside of the atom.

The electronic hypothesis in this respect can be detected for field variations of the vital field, or deviations of this field in their geometry. Of fact, integral geometry elements are incorporate to explain and determine this field deviation for their energy spectra. There is a report of these talks in the Current Medical Chemistry Journal [current], which has included the most famous scientific reports in advanced research in medicine and their different areas. In this important and prestige journal is included a complete scientific report in nano-medicine [28].

Here is planted the possibility of cure through the energy scanner of the human body to different organic systems using their different spectral resonances.

The research developed through different and various papers [29–31] shows through advanced mathematics the interchange of particles required to spill in the damaged part of the body of the photons required to correct information of their atoms. Then is corrected and restored the vital field and with it we achieve the obtaining of cure. He uses a version of the Feynman integrals to explain the interchanges and actions through the energy paths of the particles (see the figure 4).

Figure 3. A). Liquid light to help to the development of future advanced electronics in the threshold of the spintronics in the transducers design.  B). Direct sum of H-states to establish the curvature energy by the field ramification. C). Surface of energy E(k₁, k₂), to a metallic structure whose energy and prohibit trenches of energy in the solid were obtained applying a elementary electric charge that produce a planar constant superconductivity [20, 22–25].

Figure 4. Nanomedicine research based in quantum field theory [59, 60].

However, these researches were beyond the organic sufferings arriving to the conclusion that all suffering or illnesses have an origin metal in the mind-body. Likewise, is concluded in a research presented in an international conference [30] that “…all is reduced to correct and recover The WILL…”, “…the will is all”.

A graph is showed on the possible correction and restoring of the will compensating the energy displacement required by the cure (see figure 5).

Figure 5. Fill of incomplete atoms with free spaces for lack of one electron even of the order of their Fermi energy ∈_F. This distribution is analyzed for the mono-pharmacist Pulsani considering an analytic electromagnetic potential ϕ(x) = x²(1–e^–x)log(x), [=nJ].

By the property recognize + displacement = ϕ(1)δ(0 – 1) + δ(1)u(0) (Theorems F. Bulnes applied to nano-medicine and radionics) with an evolution change given by exp(tX), we have the curve of recovering of the will. This graph corresponds to the action of Pulsani quantum mono-pharmacists. The continuous strengthen of the will [30].

Now recently have been realised an incursion on possible photonics and radionics developments on bio-medical devices adding research of photonics and spintronics, from the QED (Quantum Electrodynamics) and recent results in theoretical physics obtained and published in archival physics.

Likewise, is published an important theory of these devices linked with the study of some quantum complements and organic metal complements rich of certain class of photons that enrich the cure power and action of mono-pharmacists in quantum medicine and nano-medicine. In this research are explained possible mechanism to cure any illness from quantum level (figure 60).

A problem that has been presented in these researches is the fine nanometric gauging of quantities of the energy that can be registered in electronics devices, because these devices to experiments have been not invented yet. However, are established at least in design level possible quantum electronic devices to the correction, detection and alignment of energy fields of the human body [29–32].

References

1. F Bulnes, FH Bulnes-González, E Álvarez, J Maya, F Monroy (2010) Integral Medicine: New Methods of Organ Regeneration by Cellular Encoding through Path Integrals Applied to the Quantum Medicine Journal Nanotechnol. Eng. Med 1: 031009.
2. F Bulnes, J Maya,  I Martínez (2012) Design and Development of Impeller Synergic Systems of Electromagnetic Type to Levitation/Suspension Flight of Symmetrical Bodies. Journal of Electromagnetic Analysis and Applications 1: 42–52.
3. F Bulnes, FH Bulnes, E Hernández, J Maya (2011) Diagnosis and Spectral Encoding in Integral Medicine through Electronic Devices Designed and Developed by Path Integrals. Journal of Nanotechnology in Engineering and Medicine ASME 021009: 10.
4. F Bulnes, S Fominko (2016) Dx-Schemes and Jets in Conformal Gravity using Integral Transforms. International Journal of Mathematical Research 2: 154–165.
5. Bulnes F (2015) QED-Lie Algebra and their Modules in Superconductivity. Journal of Applied Mathematics and Physics. 3: 417–427.
6. F Bulnes (2015) Local Diffeomorphisms and Smooth Embeddings to Gravitational Field II: Spherical Symmetry and their Breaking in the Space-Time. Physics and Astronomy International Journal 2: 00045.
7. Francisco Bulnes (2015) Mathematical Electrodynamics: Groups, Cohomology Classes, Unitary Representations, Orbits and Integral Transforms in Electro-Physics. American Journal of Electromagnetics and Applications 6: 43–52.
8. LJ Mason, J Frauendiener (1990) Sparling 3-form, Ashtekar variables and quasi-local mass, Twistor in Mathematics and Physics, Cambrindge, UK, 1990.
9. F Bulnes, Y Stropovsvky, I Rabinovich (2017) Curvature Energy and Their Spectrum in the Spinor-Twistor Framework: Torsion as Indicium of Gravitational Waves. Journal of Modern Physics 8: 1723–1736 2017.
10. F Bulnes (2015) Integral Transforms and Opers in the Geometrical Langlands Program. Journal of Mathematics1: 2015.
11. Bulnes F Integral geometry methods on deformed categories to geometrical Langlands ramifications in field theory, Ilirias Journal of Mathematics 3: 1–13.
12. Bulnes F (2014) Design of Quantum Gravity Sensor by Curvature Energy and their Encoding. IEEE Proc, SAI 2014, London, UK Pg: 855–861.
13. Francisco Bulnes (2013) Quantum Intentionality and Determination of Realities in the Space-Time Through Path Integrals and Their Integral Transforms, Advances in Quantum Mechanics, Prof. Paul Bracken (Ed.), InTech.
14. Francisco Bulnes (2017) Detection and Measurement of Quantum Gravity by a Curvature Energy Sensor: H-States of Curvature Energy, Recent Studies in Perturbation Theory, Dr. Dimo Uzunov (Ed.), InTech.
15. Bulnes F, Bulnes FH, Cote D (2012) Symptom Quantum Theory: Loops and Nodes in Psychology and Nanometric Actions by Quantum Medicine on the Mind Mechanisms Programming Path Integrals, Journal of Smart Nanosystems in Engineering and Medicine 1: 97–121.
16. Bulnes F, Álvarez A (2013) Homological Electromagnetism and Electromagnetic Demonstrations on the Existence of Superconducting Effects Necessaries to Magnetic Levitation/Suspension. Journal of Electromagnetic Analysis and Applications 5: 255–263.
17. Mahmoud J, Hashim S (2015) Principles of Superconducting Spintronic Device to Generate Fermionic Orbital Spaces. Journal on Photonics and Spintronics 4: 1 USA.
18. Bulnes F (2013) Mathematical Nanotechnology: Quantum Field Intentionality. Journal of Applied Mathematics and Physics 1: 25–44.
19. Bulnes F (2015) Curvature Spectrum to 2-Dimensional Flat and Hyperbolic Spaces through Integral Transforms. Journal of Mathematics RP 1: 1 USA.
20. Bulnes F, Martínez I, Mendoza A, Landa M (2012) Design and Development of an Electronic Sensor to Detect and Measure Curvature of Spaces Using Curvature Energy. Journal of Sensor Technology 2: 116–126.
21. Mahmoud J (2013) Spintronics in Devices: A Quantum Multi-Physics Simulation of the Hall Effect in Superconductors. Journal on Photonics and Spintronics 2: 1 USA.
22. Bulnes F, Martínez I, Zamudio O (2016) Fine Curvature Measurements through Curvature Energy and their Gauging and Sensoring in the Space, Advances in Sensors Reviews 4, (Ed.) Sergey Y. Yurish, IFSA.
23. Bulnes F, Humeini S (2018) Topological Superconductors Characterizing II: Curvature Energy in Hall-Spintronics Developments, SciFed Journal of Spintronics and Quantum Electronics, 1: 1.
24. Bulnes F (2016) Electromagnetic waves in conformal actions of the group SU (2,2), on a dimensional flat model of the space-time. VI International Conference “Geometry, Dynamics, Integrable Systems”-GDIS, Izhevsk, Russia.
25. Prof. Dr. Francisco Bulnes (Editor-in-Chief.) (2018) Mini-Workshop on Nanoparticles, Photonics and Advanced Electronics. Journal on Photonics and Spintronics Chalco, State of Mexico.
26. Bulnes F (2017) Extended d- Cohomology and Integral Transforms in Derived Geometry to QFT-equations Solutions using Langlands Correspondences. Theoretical Mathematics and Applications 7: 51–62.
27. Bulnes F (2014) Derived Categories in Langlands Geometrical Ramifications: Approaching by Penrose Transforms. Advances in Pure Mathematics 4: 253–260.
28. Bulnes F (2012) Combination of Quantum Factors in Integral Mono-pharmacists and their Actions in Cellular Regeneration and Total Cure, Current Medicinal Chemistry International Conference of Drug Discovery and Therapy 2012 Reports, Bentham Science, Dubai, UAE, 2012.
29. Bulnes F, Bulnes FH, Hernandez E (2010) Integral Medicine: New Methods of Organ-Regeneration by Cellular Encoding through Path Integrals applied to the Quantum Medicine. Journal of Nanotechnology in Medicine and Engineering 1: 7.
30. Bulnes F (2013) The Anxiety Factor in the Dimension of the Symptom Space and their Elimination for Nano-Metric Actions of Quantum Mono-Pharmacists,” Drug Discovery and Therapy World Congress 2013, 3–6 June, Boston Massachusetts, USA, 2013.
31. Bulnes F, Bulnes-Gonzalez FH (2014) Quantum Developments in Nanomedicine: Nanocurative Actions by Soft Photons Sources and their Path Integrals. Nanomedicine  Open Central Press, UK, Pg: 238–267.
32. Bulnes F (2015) Photonic Chains of Wave-links to the Quantum Communication. Journal on Photonics and Spintronics 3: 10–14.

^[1] Exists a research programme called electrodynamics research programme, which is dedicated to the future technologies whose fundamentals are the quantum and classical electrodynamics including the modern developments in advanced electronics.

^[2] I am Editor-in-Chief of the Journal on Photonics and Spintronics, in USA. See: http://researchpub.org/journal/jps/editorial%20board.html