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This paper extends previous work on liquid-crystal-display-based angle-of-arrival (AoA) estimation, initially performed for only a single light source (LS), by considering scenarios with multiple LSs. First, the system model is revisited to investigate parameters that influence detection of multiple LSs. Next, challenges such as separation of co-located LSs and ambiguities are investigated. It is identified that target separation gets increasingly challenging with decreasing distance between LSs, and AoA estimation developed for a single LS leads to ambiguities in scenarios with multiple LSs. These problems are solved by a novel angular separation algorithm and dedicated intensity measurements. Finally, two new experimental setups are introduced to investigate and model optical diffraction effects, and to verify theoretical derivations by measurement results.

We have proposed a structural design for a single photon avalanche diode with a low breakdown voltage. This diode is fabricated using Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 μm HV CMOS technology, and it can maintain a high operating excess voltage in an n-on-p design without requiring any additional customized well layers. The n-on-p type device is particularly advantageous for a 3D-stacked backside illuminated structure and offers excellent photon detection capabilities at longer wavelengths. By incorporating a high doping concentration PDD well layer, we can significantly increase the excess bias, resulting in enhanced photon detection probability in the near-infrared wavelength range, all while maintaining a lower voltage due to a reduction in breakdown voltage. This design also leads to power consumption savings. As a result, our designed device is well-suited for consumer applications such as 3D image rendering and LiDAR technology.

Ga2O3 is an ultra-wide band semiconductor corresponding to the deep ultraviolet(UV) spectrum, which can be used to prepare solar-blind UV detectors. The solar-blind ultraviolet detectors are widely used in military and aerospace fields dueto strong anti-interference ability, high detection sensitivity and low background noise.The basic properties of Ga2O3 materials, including different crystal structures and their preparation, and the recent progress in solar-blind UV detectors based on Ga2O3 were introduced in this paper. Among them, metal-semiconductor-metal (MSM) structure of Ga2O3 devices are the most common, which are expected to achieve business application with commercial parameters. The Ga2O3-based heterostructure and Schottky detectors also exhibit excellent performance and self-supply characteristics. In addition, Ga2O3 devices based on thin film transistor become a potential solar-blind ultraviolet detector. They combine the working mechanism of MSM and transistor structure to obtain high light gain, which are suitable for weak signal detection.

In the present work, SnS thin films were prepared using the CBD technique at room temperature and varying annealing temperatures from 300 to 450 °C for photo detector applications. The prepared samples were characterized using different techniques for analyzing the structural, optical, morphological, and photo sensing properties of the samples. From XRD analysis, the diffraction pattern of all the prepared thin films shows the pristine SnS phase of the samples possessing an orthorhombic phase without the presence of any impurity phases. Among the fabricated thin films, the SnS thin film annealed at a temperature of 350 °C reveals the highest crystallite size. The Raman results showed the vibrational modes of SnS films and with the increase in growth temperature, the peaks are slightly shifted towards the lower wavelength region. Morphological results show that the SnS thin films exhibit a uniform morphology of 2-D petal-like morphology with different sizes. The UV-vis spectroscopic study shows the decrease in the bandgap value of the samples with the increase in annealing temperature. The photo sensing properties of the fabricated samples show the SnS sample annealed at 400 °C has a higherresponsivityvalueof6.40×10-2AW-1, external quantum efficiency(EQE)value of 14.9%, and the detectivity value of 6.05 × 109 Jones. Finally, the transient photo response results suggest that the SnS annealed at 350 °C shows a rise and fall time of 1.5 and 2.5 s compared to the othersampleswhichwouldbebettersuitedforphotodetectorapplications. The electrical conductivity and photo-conductivity of the films increase by more than two orders with increase of film thickness from 170 nm to 915 nm. Hall Effect measurements confirm the p-type nature of the as-prepared SnS thin films. [ABSTRACT FROM AUTHOR]

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Two-dimensional (2D) materials possess exceptional physical and chemical properties, making them promising for various applications in electronic and optoelectronic devices. In this study, nanohybrids of 1D NiSe on different weight percentages (wt %) of 2D g-C3N4 (0%, 1%, 3%, and 5%) were synthesized using a hydrothermal method. The structural, morphological, and optical properties of the synthesized hybrid sample were thoroughly investigated using various basic characterization techniques such as XRD, SEM, TEM, UV–Vis, Photoluminescence, N2 adsorption–desorption, and XPS. The resulting hybrid material exhibited a high aspect ratio, few stacking layers, a considerable surface area, and an increased band gap, indicating its potential for optoelectronic applications. The exceptional physical and chemical properties of two-dimensional (2D) materials make them highly promising for various applications in electronics and optoelectronics devices. The UV–Vis analysis revealed that the 5%wt g-C3N4/NiSe hybrid material demonstrated the highest absorption and the smallest optical band gap of 2.30 eV, indicating its suitability for photo-sensing applications. The I-V characteristics analysis of the synthesized nanoparticles with an applied voltage of ± 4 V revealed an improvement in the 3 and 5 wt% g-C3N4/NiSe samples, attributed to the increase in injected charge density. Furthermore, the diode created using the 5 wt% composite showed a maximum barrier height (Φb) of 0.79 eV when subjected to xenon lamp light irradiation, demonstrating its potential for utilization in the upcoming optoelectronics industry. [ABSTRACT FROM AUTHOR]

We investigate the optical and electronic characteristics of parental MnNiGe and doped MnNi 1-x Ag x Ge (x = 4 %, 8 %, and 12 %) for photodetector and other electronic applications. First principles are applied to every calculation performed in the context of DFT. The generalized gradient approximation with the Hubbard potential included (GGA + U) has been chosen as the appropriate approximation to handle systems with strongly coupled electrons. The semi-metallic parental MnNiGe and doped MnNi1 -x Ag x Ge (x = 4 %, 8 %, and 12 %) is ideal for conducting materials in electronics due to band overlapping, according to our findings. Degenerate doping of Ag into MnNiGe includes spinning the Fermi level, changing the DOS profile, and reducing the density of Fermi level states that allow tunneling from the valence band to the conduction band. An important part of this research is analyzing the refractive index, reflectivity, extinction coefficient, dielectric function, absorption coefficient, and energy loss function of parental MnNiGe and doped MnNi 1-x Ag x Ge (x = 4 %, 8 %, and 12 %). According to our findings, it is possible to create a photo detector based on MnNi 1-x Ag x Ge (x = 4 %, 8 %, and 12 %) that can detect light in the visible range (below 500 nm). It has also been found that the MnNi 1-x Ag x Ge (x = 4 %, 8 %, and 12 %) exhibits the highest sensitivity to light with a wavelength of 450 nm. Due to its advantageous optical characteristics in the visible and ultraviolet regions, this material could be useful for the development of numerous optoelectronic applications. • The study applies first principles and DFT with GGA + U approximation to investigate the structural and optoelectronic properties of MnNi1-xAgxGe alloys with Ag doping concentrations of 4 %, 8 %, and 12 %, highlighting potential applications in photodetectors and other electronic devices. • It presents a detailed analysis of the impact of non-magnetic silver doping at the nickel site, showing a transition to semi-metallic behavior and modifications in electronic band structure, resulting in no band gap and a potential increase in conductivity and optoelectronic functionality. • The research concludes that doped MnNi1-xAgxGe alloys exhibit enhanced optical properties, such as a higher sensitivity to visible light, particularly at 450 nm, making them suitable for the development of new optoelectronic devices. [ABSTRACT FROM AUTHOR]

Perovskite materials are considered as the most alluring successor to the conventional semiconductor materials to fabricate solar cells, light emitting diodes and electronic displays. However, the use of the perovskite semiconductors as a channel material in field effect transistors (FET) are much lower than expected due to the poor performance of the devices. Despite low attention, the perovskite FETs are used in widespread applications on account of their unique opto-electrical properties. This review focuses on the previous works on perovskite FETs which are summarized into tables based on their structures and electrical properties. Further, this review focuses on the applications of perovskite FETs in photodetectors, phototransistors, light emitting FETs and memory devices. Moreover, this review highlights the challenges faced by the perovskite FETs to meet the current standards along with the future directions of these FETs. Overall, the review summarizes all the available information on existing perovskite FET works and their applications reported so far. [ABSTRACT FROM AUTHOR]

CMOS single-photon avalanche diode (SPAD) array is a high-timing-resolution photon-counting image sensor. Pixel size shrinkage for high image resolution is highly desirable but hindered by the lowered photon-detection-probability (PDP) as the edge area becomes significant. We propose and demonstrate a parameter-free method for simulating PDP with the edge effect. Considering the doping profile, electric field, photon generation, and trigger probability distributions in two dimensions, the PDP reduction at the device edge is analyzed in a quantitative way. Besides, a novel guard-ring design for enhancing PDP of small SPAD has been proposed and simulated by our method. A threefold enhancement was obtained with the newly designed guard-ring structure compared with the original one. Our work is useful for developing small-pitch SPAD array for high-resolution imaging applications. [ABSTRACT FROM AUTHOR]

In this paper, the calculations for determining the optical response of GaAsSb/InGaAs based photo detector have been performed and the results have been analysed successfully. The k.p model has been used to identify the behaviour of wave functions of the charge carriers and their discrete energy states. Finally, in optical response of the designed heterostructure, the optical absorption coefficient of the heterostructure has been computed. The computed results shows that the designed GaAsSb/InGaAs based heterostructure can be functional in designing the photodetectors operating in MIR (mid infrared) regions. [ABSTRACT FROM AUTHOR]

A method of direct measurement of the observer's velocity (peculiar velocity) relative to the accompanying reference system is proposed and investigated. To measure peculiar velocity, it is proposed to use the measurement of stellar light aberration. A comparison of the use of light aberration and the Doppler Effect for measuring velocity relative to relic radiation was made. When using the Doppler Effect, the total speed of the observer was measured - the Hubble speed and the radial component of the peculiar speed of the observer. As a result of the analysis of the components of the observer's velocity in the comoving reference frame, the Hubble and peculiar velocities of the observer, their essential features are formulated. The analysis of the shape of the wave fronts of the CMB radiation, the radiation of quasars, the radiation of stars and the radiation of ground sources is given. As a consequence of this analysis, the decisive influence of the shape of their wave fronts on the possibilities of measuring stellar aberration and the absence of such an effect when measuring velocity using the Doppler Effect are shown. Measurement of light aberration in an inertial system enables direct measurement of the observer's peculiar velocity in an comoving reference frame. Knowing the observer's peculiar velocity is important for increasing the accuracy of determining the Hubble velocity of especially objects of relatively small remoteness. The proposed structures of devices for measuring the peculiar velocity of an inertial reference system were investigated. Peculiar speed is determined by the measured light aberration without switching to another frame of reference. Their expected accuracy and reliability were evaluated. The practical use of the proposed structures is possible in astronomy and spacecraft.

Wavelength division multiplexing (WDM) technique plays a vital role in optical fiber communication. In this paper, a 4 × 1 WDM system has been developed with Vertical Cavity Surface Emitting LASER as optical source for each input. The performance analysis has been carried for Non Return to Zero (NRZ), hyperbolic secant, Gaussian and impulse generators over complex WDM optical fiber up to 50 km with less attenuation of 0.2 dB/Km. The Signal to noise ratio of received signal through Avalanche Photo diode in the receiver is calculated. This work identifies the best pulse generator with reduced noise performance suitable for the proposed system. The proposed system is modeled in optisys13 and insightful discussions are provided from the simulated results. [ABSTRACT FROM AUTHOR]

Perovskite materials are considered as the most alluring successor to the conventional semiconductor materials to fabricate solar cells, light emitting diodes and electronic displays. However, the use of the perovskite semiconductors as a channel material in field effect transistors (FET) are much lower than expected due to the poor performance of the devices. Despite low attention, the perovskite FETs are used in widespread applications on account of their unique opto-electrical properties. This review focuses on the previous works on perovskite FETs which are summarized into tables based on their structures and electrical properties. Further, this review focuses on the applications of perovskite FETs in photodetectors, phototransistors, light emitting FETs and memory devices. Moreover, this review highlights the challenges faced by the perovskite FETs to meet the current standards along with the future directions of these FETs. Overall, the review summarizes all the available information on existing perovskite FET works and their applications reported so far.

Indium Selenide (InSe) is the most suitable photovoltaic conversion material with narrow band gap (1.3 eV) in the layered semiconductors. The optical and transport properties of InSe offer significant potential for promising applications in the modern era of electronics and photo-electronic devices. The aim is achieved by high electric conductivity of InSe crystals, Sb x In 1 − x Se (x= 0.00, 0.10, 0.15, 0.20) crystals was grown by direct vapour transport (DVT) technique. The chemical compositional and surface morphology properties of grown crystals were studied by energy dispersive X-ray analysis (EDAX) and scanning electron microscope (SEM) respectively. The hexagonal crystal structure of grown crystal has revealed by X-ray diffraction (XRD) spectra. The dopant concentration of antimony (Sb) was found to have a decreasing effect on the optical band gap and activation energy as calculated through absorption spectra and Arrhenius relations respectively. The photo-response parameters: growth-decay and trap-depth parameters have been obtained using growth-decay curve. These results confirm that Sb x In 1 − x Se crystal was collective applicant for electronic and optoelectronic devices. [Display omitted] • The high-quality InSe and Sb x In 1 − x Se crystals were successfully grown using the direct vapor transport (DVT) technique. • Hexagonal crystal structure of grown pristine and Sb doped InSe crystals confirmed via X-ray diffraction (XRD) spectral analysis. • The obtained direct optical band gap varies from 1.30 eV to 1.17 eV. • Pulse photo response of crystal based photo detector have been analyzed and comprehensive analysis of photo detection parameters were carried out. • The obtained results strongly support the potential application of Sb x In 1 − x Se crystals in switching and optoelectronic devices. [ABSTRACT FROM AUTHOR]

We present the design and application of a $64\times 64$ pixel SPAD array to portable colorimetric sensing, and fluorescence and x-ray imaging. The device was fabricated on an unmodified 180 nm CMOS process and is based on a square p+/n active junction SPAD geometry suitable for detecting green fluorescence emission. The stand-alone SPAD shows a photodetection probability greater than 60% at 5 V excess bias, with a dark count rate of less than 4 cps/ $\mu \text{m}^{\mathbf {2}}$ and sub-ns timing jitter performance. It has a global shutter with an in-pixel 8-bit counter; four 5-bit decoders and two 64-to-1 multiplexer blocks allow the data to be read-out. The array of sensors was able to detect fluorescence from a fluorescein isothiocyanate (FITC) solution down to a concentration of 900 pM with an SNR of 9.8 dB. A colorimetric assay was performed on top of the sensor array with a limit of quantification of $3.1~\mu \text{m}$. X-rays images, using energies ranging from 10 kVp to 100 kVp, of a lead grating mask were acquired without using a scintillation crystal. [ABSTRACT FROM AUTHOR]

• High quality of ZnO low dimensional systems were grown by a simple chemical route. • The morphology of ZnO materials were tuned by varying the precursor concentration. • Variation in precursor concentration induces a structural change in ZnO. • The crystallinity of ZnO material improves by tuning the precursor concentration. • The I-V plot of nanostructure ZnO device found to be useful for UV photo detection. We establish a simple approach to control the morphology of ZnO materials, by using chemical bath deposition (CBD) technique. The effect of variation in precursor concentration on the morphology and crystalline characteristics are investigated by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. Morphological effect on the current – voltage (I-V) characteristic of ZnO nanostructure and microstructure devices are investigated. Nanostructure ZnO devices show an enhancement in the forward bias current in comparison to microstructure devices. Further enhancement in photocurrent under ultraviolet (UV) light for nanostructure ZnO devices demonstrate the capability of a potential UV photo detector. [ABSTRACT FROM AUTHOR]

[Display omitted] • This research work pristine Bi 2 S 3 , Bi 2 S 3 :Cu2%, Bi 2 S 3 :La2%, and Bi 2 S 3 :Cu2%:La2% thin films were prepared by nebulizer spray pyrolysis. • The morphological studies using FESEM analysis showed the unformed distribution of small grains. • The optical absorbance spectra of the thin films were observed from the wavelength of 350 nm to 1000 nm. • films were subjected to analyzing U.V. photosensing properties. As a result, maximum responsivity (1.24 × 10−01 AW−1), detectivity (1.13 × 1010 Jones), and EQE (40%) were achieved for Bi 2 S 3 :Cu: La-sample. Nowadays, chalcogenide-based thin layers are proving a promising light-absorbing material with low cost and are technologically suitable for light to current conversion applications. In this study, for the first time, pristine Bi 2 S 3 , Bi 2 S 3 :Cu2%, Bi 2 S 3 :La2%, and Bi 2 S 3 :Cu2%:La2% thin films were prepared by nebulizer spray pyrolysis technique on a glass substrate at 300 °C. The obtained XRD pattern confirms the orthorhombic structure of Bi 2 S 3 and possesses a maximum crystallite size of 38 nm for Bi 2 S 3 :Cu: La co-doped sample. Images taken with a FESEM analysis showed the unformed distribution of round shaped grains without any cracks and co-doping leads to the development of slight cluster formation. The optical absorbance spectra of the thin films were observed from the wavelength of 350 nm to 1000 nm, and the co doping process highly strengthen the optical absorbance, which is prerequisite for an efficient photodetector. A lower band gap value of 1.7 eV is achieved for Bi 2 S 3 : Cu: La thin film. From PL studies, defect emission bands around ∼325 and 525 nm related to band edge emission and sulfur vacancies are obtained. Further, UV photosensing properties of each sample were evaluated. Commendable performance with maximum responsivity (1.24 × 10−1 AW−1), detectivity (1.13 × 1010 Jones), and EQE (40%) were achieved for Bi 2 S 3 :Cu:La-sample. The enhanced figures-of-merit are attributed large crystalline size, good crystallinity, lower bandgap and crack free surface. The photo sensing results may widen the field of photosensing application. [ABSTRACT FROM AUTHOR]

Quantum well infrared photodetector (QWIP) become one of the important devices recently for their efficient, stability,uniformity, and high intrinsic speed. The photodetector was designed, and the validity, absorption coefficient, and band transitions are studied extensively. The quantum wells included in this research operate in mid infrared wavelength region (9-11 µm). Results showed that peak absorption coefficient at (10.6 μm) is (9000 cm-1) for Bound – bound transition and is more narrow and intense from boundcontinuum transition (1800 cm-1) and the quantum well based devices can be used to detect such wavelength providing that the external electric field stays below a reasonable value. This makes such device a promising solution for MIR applications

Abstract The main parameters of microchannel amplifiers – angular and energy distributions of photo- and secondary-electron emission – are determined by the emission properties of materials. These parameters depend on the type of materials, the thickness of deposited films and the technology of processing their surfaces. Data on the emission properties of materials can be obtained by means of experimental measurements or by calculation methods using molecular dynamics. In both cases, this is associated with significant resource costs. In the cases where some of these characteristics of the materials are unknown, a calibration procedure can be recommended to determine them. Details of this procedure are described in this paper. Comparison of numerical and experimental data for specific devices is performed. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated and simulated the interface between indium antimonide and the passive layer in an infrared detector. One of the most important problems in this detector is its large dark current. We have explained the factors affecting the dark current and examined their effects using numerical analysis. One of the most important and influential factors in this process is the presence of defects in oxide. We have investigated the defect in the SiO2 trap. The impact of acceptor and donor traps, such as density and energy levels has been investigated, and then the defects of constant positive and negative steady-state charges as important factors in the current have been analyzed. We examined the darkness current and finally tried to improve it with a proposed structure. The dark current for a 0.5 V reverse bias was decreased from 2.07 mA/μm 2 to 0.504 mA/μm 2 . [ABSTRACT FROM AUTHOR]

The primary objective of this work is image processing based blood groups identification that utilizes the digital image matching process without using needles. Now-a-days, the blood group testing uses needles and also utilizes some chemicals, optical plates, cotton cloths, etc. Above biomaterial disposal in the environment is very dangerous and also creates environmental soil pollution. Non-bio degradable materials are the main pollution sources in soil. Technology and various researches have dominated to save human blood and to control the soil pollution and thus the present situation is met. The novel blood group testing is done by finding blood group of a patient without piercing the skin. This article explains a method to determine the human blood type by applying digital image processing to understand the image of artificial vessels underlying the skin. The research includes Multicore wavelength light sprinkling method, where light passes through the vessels for classifying the blood cells based on exact antigens on the red blood cell surface. The transferrable camera along with photo-detectors forms the basic detector structure and is used to detect the light distribution produced by blood cell to determine the blood type. This research presents a current state-of-the-art in optimizing digital image processing based blood group identification, which provides a clear vision of the latest top research advances in image processing with the help of MatLab and Embedded C program. [ABSTRACT FROM AUTHOR]

Microwave photonics system provides high bandwidth capabilities of fiber optic systems and also contains the ability to provide interconnect transmission properties, which are virtually independent of length. In this paper, we have studied the effect of higher order dispersion, harmonic suppression of forth order with different modulation values. We found that, higher order harmonic suppression and frequencies are varying with the electrical drive signal for different modulation depths. It is apparent from the calculated result that the harmonic suppression increases as the modulation depth increases. In all the case, it is observed that the harmonic suppression is varying, but the frequencies are same for different values of depth of modulation. The analysis performed by the other researchers describes that, harmonic suppression varies with frequency. But in our analysis, we found that harmonic suppression is independent of frequency. Thus, it can be beneficial; as electric signal is stable over the tuning band. In this paper, we derived the step by step expression for harmonic suppression for better understanding. [ABSTRACT FROM AUTHOR]

Microwave photonics system provides high bandwidth capabilities of fiber optic systems and also contains the ability to provide interconnect transmission properties, which are virtually independent of length. The low-loss wide bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. So, we can considered microwave photonics as the field that studies the interaction between microwave and optical waves for applications such as communications, radars, sensors and instrumentations. In this paper we have thoroughly reviewed the microwave generation techniques by using photonics technology. [ABSTRACT FROM AUTHOR]

A novel technique to generate an arbitrary chirped waveform by harnessing features of lithium niobate (LiNbO3) Mach-Zehnder modulator is proposed and demonstrated. The most important application of chirped microwave waveform is that, it improves the range resolution of radar. Microwave photonics system provides high bandwidth capabilities of fiber-optic systems and also contains the ability to provide interconnect transmission properties, which are virtually independent of length. The low-loss wide bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. So, it should be consider that microwave photonics as the field that studies the interaction between microwave and optical waves for applications such as communications, radars, sensors and instrumentations. In this paper, we have thoroughly reviewed the arbitrary chirped microwave generation techniques by using photonics technology. [ABSTRACT FROM AUTHOR]

Light Fidelity (Li-Fi) is one of the future technologies in wireless communication sector. Li-Fi refers to 5G Visible Light Communication (VLC) systems using light-emitting diodes as a medium to high-speed communication in a similar manner as Wireless-Fidelity (Wi-Fi). These days when Internet has become a major attraction, people are in need of Wi-Fi hotspots. Li-Fi or New Life of data communication is a better alternative to Wi-Fi in wireless communication. This paper proposes a survey on Li-Fi technology. Li-Fi has more capacity in terms of bandwidth in visible region, therefore it does not poke its nose in other communication which uses radio frequency range without taking its frequency bands. Li-Fi has thousand times greater speed than Wi-Fi and provides security as the visible light is unable to penetrate through the walls, which proposes a new era of wireless communication. The concept of Li-Fi is data communication on fast flickering of light which is not detected by human eye but it is focused on photo detector which converts the on-off state into binary digital data. [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and test of an InGaAs avalanche photodiode (APD) for 950–1650 nm wavelength sensing applications. The APD is grown by molecular beam epitaxy on InP substrates from lattice-matched InGaAs and InAlAs alloys. Avalanche multiplication inside the APD occurs in a series of asymmetric gain stages whose layer ordering acts to enhance the rate of electron-initiated impact ionization and to suppress the rate of hole-initiated ionization when operated at low gain. The multiplication stages are cascaded in series, interposed with carrier relaxation layers in which the electric field is low, preventing avalanche feedback between stages. These measures result in much lower excess multiplication noise and stable linear-mode operation at much higher avalanche gain than is characteristic of APDs fabricated from the same semiconductor alloys in bulk. The noise suppression mechanism is analyzed by simulations of impact ionization spatial distribution and gain statistics, and measurements on APDs implementing the design are presented. The devices employing this design are demonstrated to operate at linear-mode gain in excess of 6000 without avalanche breakdown. Excess noise characterized by an effective impact ionization rate ratio below 0.04 were measured at gains over 1000.

We report the evaluated results of an optical exclusive OR (XOR) circuit for high-speed binary signals, which operates based on balanced detection and intensity modulation. This circuit partly adopts simple electronics in order to achieve simple configuration and operation. Two input optical binary signals into a balanced photo detector produce an electrical signal for directly driving a modulator. The modulator modulates the lightwave from a laser diode and generates optical XOR output of the two input optical signals. After briefly explaining its configuration and operating principle, We demonstrate some experimental results to show its potential. We show its successful operation at 40 Gbit/s binary signals including bit error rate measurement.

In this research we studying the sensitivity of a porous silicon photo detector, wefound it improved through rapid thermal oxidation processes. Under our optimumpreparation conditions, photocurrent can reach about 3408 μA (under power density 100mW/cm2 tungsten lamp illumination) and dark current is about 300μA(at reverse bias of 5V).

Nanorods (NRs) of crystalline ZnO coated with thin layers of TiO 2 (ZnO@TiO 2) were fabricated with the help of spin coating technique followed by hydrothermal method. Scanning electron microscopy (SEM) and X-ray diffraction analysis confirms the morphology and structural stability of as-prepared NRs. The optical band gaps of the NRs were estimated, and a clear blue-shift towards the UV region has been detected. When UV light falls on as-prepared device (i.e., in the "ON" state), a significant increase in photocurrent (I UV) at zero voltage supply was observed from 6 µA to 17 µA, while in the "OFF" state, the dark current (I dark), increases from 0.08 µA to 0.6 µA with ZnO@TiO 2 NRs as compared to bare ZnO NRs respectively. Responsivity and detectivity of TiO 2 coated ZnO NRs based device found maximum in UV region unlike bare ZnO NRs. Enhanced photocurrent achieved by the growth of TiO 2 layers on ZnO NRs is 250 µA as compared to bare ZnO NRs for which it is 35 µA at 10 V voltage supply under the ultraviolet irradiation (illumination intensity of 1 mW/cm2). Furthermore, theoretical calculations have been performed using the first-principles density-functional theory to understand the effects of heterostructure NRs on the electronic and optical properties of TiO 2 coated ZnO. [Display omitted] • Nanorods (NRs) of crystalline ZnO coated with thin layers of TiO2 (ZnO@TiO2) were fabricated with the help of spin coating technique followed by hydrothermal method. • Enhancements in photoconductivity, responsivity and detectivity were observed with ZnO@TiO2 NRs as compared to bare ZnO NRs. • Theoretical calculations have been performed using the density functional approach (DFT) to understand the effects of confinement and coating of TiO2 on bare ZnO NRs. [ABSTRACT FROM AUTHOR]

During field trials, it was observed that the delay of ignition of electro-explosive devices (EED) depends on ratings of power supplies or dynamo and also on the firing cable lengths. The change in ignition delay of EEDs due to altered supplied current will detoriate the repeatability of sequence of actions in time-critical armament applications. In order to study, supplement and analyze this observation, the measurement of electrical energy required for EEDs ignition is necessary. The electrical energy of EEDs has been determined experimentally by instrumentation and measurement setup using hall sensor and photo detector. The hall sensor is used to measure the actual current passing through EEDs when power supply is applied to them. Photo detector is used to detect the flash produced during EED ignition. By conducting repeated trials, it was observed that this method is reliable to determine the electrical energy required for EEDs ignition. With this parameter, the actual current to be supplied and the pulse width of supplied current for repeated ignition delays can be determined. Knowing the electrical energy of a particular EED by the proposed method, the required firing cable length and power supply for ignition of critical delay applications can be selected. This method also helps to design explosive-based ignition systems in defence applications.

During field trials, it was observed that the delay of ignition of electro-explosive devices (EED) depends on ratings of power supplies or dynamo and also on the firing cable lengths. The change in ignition delay of EEDs due to altered supplied current will detoriate the repeatability of sequence of actions in time-critical armament applications. In order to study, supplement and analyze this observation, the measurement of electrical energy required for EEDs ignition is necessary. The electrical energy of EEDs has been determined experimentally by instrumentation and measurement setup using hall sensor and photo detector. The hall sensor is used to measure the actual current passing through EEDs when power supply is applied to them. Photo detector is used to detect the flash produced during EED ignition. By conducting repeated trials, it was observed that this method is reliable to determine the electrical energy required for EEDs ignition. With this parameter, the actual current to be supplied and the pulse width of supplied current for repeated ignition delays can be determined. Knowing the electrical energy of a particular EED by the proposed method, the required firing cable length and power supply for ignition of critical delay applications can be selected. This method also helps to design explosive-based ignition systems in defence applications. [ABSTRACT FROM AUTHOR]

SUMMARY Light emitting diodes (LEDs) are now used for lighting and illumination because of features such as low power consumption and long life. Lighting equipment has only LEDs, therefore it is necessary to install a photodetector to allow bidirectional communication. In this paper, we propose reception of a light signal by means of an LED for bidirectional visible light communications. We evaluate the characteristics of the LED used as a photodetector for bidirectional visible light communications through experiments. Further, we describe the newly developed experimental system that uses LEDs as a photodetector. Experiments show that an LED can be used not only as a light source but also as a photodetector for bidirectional visible light communications. [ABSTRACT FROM AUTHOR]