Photosensitive Detectors Research Articles

Design of Lidar Receiving Optical System with Large FoV and High Concentration of Light to Resist Background Light Interference.

Lidar has the advantages of high accuracy, high resolution, and is not affected by sunlight. It has been widely used in many fields, such as autonomous driving, remote sensing detection, and intelligent robots. However, the current lidar detection system belongs to weak signal detection and generally uses avalanche photoelectric detector units as detectors. Limited by the current technology, the photosensitive surface is small, the receiving field of view is limited, and it is easy to cause false alarms due to background light. This paper proposes a method based on a combination of image-side telecentric lenses, microlens arrays, and interference filters. The small-area element detector achieves the high-concentration reception of echo beams in a large field of view while overcoming the interference of ambient background light. The image-side telecentric lens realizes that the center lines of the echo beams at different angles are parallel to the central axis, and the focus points converge on the same focal plane. The microlens array collimates the converged light beams one by one into parallel light beams. Finally, a high-quality aspherical focusing lens is used to focus the light on the small-area element detector to achieve high-concentration light reception over a large field of view. The system achieves a receiving field of view greater than 40° for a photosensitive surface detector with a diameter of 75 μm and is resistant to background light interference.

Design of non-imaging receiving system for large field of view lidar

Lidar has been widely used in many fields due to its high precision. The system must also have a corresponding large field of view receiving capability in order to achieve effective detection of targets when imaging lidar realizes large-angle scanning. For the InGaAs-APD detector component, there is a contradiction between the high-frequency response bandwidth and the size of the photosensitive surface. This paper proposes a large surface four-quadrant InGaAs-APD detector with 2 × 2 area array structure design, which based on a small photosensitive panel detector with a unit diameter of 0.5 mm. On the basis of ensuring the cut-off frequency bandwidth of 100 MHz, it also realizes signal reception with large field of view and high sensitivity. For the receiving lens of the system, the relationship between the bin size of the detector and the receiving field of view in the non-imaging optical receiving system is studied. Under the condition that the parameters such as the size of the detector facet have been determined, the best position of the detector is optimally designed to maximize the receiving field of view. Based on theoretical foundations such as radiation angle coefficient and etendue, the non-imaging optical system lidar distance equation is established to evaluate the light-gathering ability of receiving lenses with different effective apertures and focal lengths, and to optimize optical structural parameters such as the best effective aperture and focal length of the receiving lens. Finally, the aspheric lens with the best parameters is selected as the basic receiving optical lens of the system, and an array type large field of view direct detection technology is proposed. The receiving optical system is composed of 6 aspheric single lenses, and the structure is in the form of 2 × 3 array, which finally realizes the efficient detection of echo signals with a large field of view of 48° × 26°.

Demonstration of a 25-picosecond single-photon time resolution with gaseous photomultiplication

Photosensitive gaseous detectors with a simple photoelectron multiplication mechanism of resistive plate chambers (RPCs) are expected to have both a large photocoverage and an excellent time resolution and to be low-cost. To demonstrate the time resolution of the RPC-based photodetectors, we built a prototype detector with a LaB6 photocathode. It was tested with a picosecond pulse laser and the intrinsic time resolution for single photons was measured to be 25.0±1.1 ps at a gain of 3.3×106.

Investigation of gamma-ray sensitivity of YAG:Ce based scintillation structures

Ionizing radiation is widely used nowadays for diagnosing and probing a wide range of objects due to the high reliability and quality of the results obtained in such research. Use of highly sensitive ionizing radiation sensors enables the reduction of the radiation dose involved in the research. Moreover, sensitive systems for monitoring environmental parameters may be also created based on such sensors. In this work, the efficiency of a low density radiation detector with the composite scintillation structure based on powdery YAG:Ce phosphor as the converting coating of photosensitive detector was investigated. The possibility to detect gamma radiation from the 241 Am and 137 Cs based sources by the ionizing radiation detector comprising YAG:Ce 3+ composite converting scintillation structure and micropixel avalanche photodiode (MAPD) was found. The number of detected gamma rays emitted by the 241 Am source was shown to increase linearly with the thickness of the composite converting scintillation structure. The thickness of the composite converting scintillation structure of 495 µm was found to enable registration of gamma-rays with the energies in the range of 26 to 662 keV.

Impact Point Determination of Gamma Interaction in a Monolithic Scintillator Crystal Read Out by a SiPM Matrix

Abstract We construct a simulation framework which can determine simultaneously deposited energy, position and time resolution of interactions of gamma rays in a monolithic scintillator crystal read out by a matrix of photosensitive detectors. And we report and discuss the simulation results form three different methods to determine the impact position of a particle.

Linearity and Optimum-Sampling in Photon-Counting Digital Holographic Microscopy

In the image plane configurations frequently used in digital holographic microscopy (DHM) systems, interference patterns are captured by a photo-sensitive array detector located at the image plane of an input object. The object information in these patterns is localized and thus extremely sensitive to phase errors caused by nonlinear hologram recordings (grating profiles are either square or saturated sinusoidal) or inadequate sampling regarding the information coverage (undersampled around the Nyquist frequency or arbitrarily oversampled). Here, we propose a solution for both hologram recording problems through implementing a photon-counting detector (PCD) mounted on a motorized XY translation stage. In such a way, inherently linear (because of a wide dynamic range of PCD) and optimum sampled (due to adjustable steps) digital holograms in the image plane configuration are recorded. Optimum sampling is estimated based on numerical analysis. The validity of the proposed approach is confirmed experimentally.

CATIROC: an integrated chip for neutrino experiments using photomultiplier tubes

An ASIC (Application Specific Integrated Chip) named CATIROC (Charge And Time Integrated Read Out Chip) has been developed for the next-generation neutrino experiments using a large number of photomultiplier tubes (PMTs). Each CATIROC provides the time and the charge measurements for 16 configurable input channels operating in auto-trigger mode. Originally designed for the light emission in water Cherenkov detectors, we show in this paper that its use can be extended to liquid-scintillator based experiments. The ∼ 26000 3-inch PMTs of the JUNO experiment, under construction in China, is a case in point. This paper describes the features of CATIROC with a special attention to the most critical points for its application to the time profile of the light emission in liquid scintillators. The achieved performances in both charge and time measurements can be inputs for future high-precision experiments making use of PMTs or other photo-sensitive detectors.

Tunable optical properties of SiO2/Ag double-layer and SiO2/Ag/SiO2 triple-layer hybrid structures

The applications of monolayer nanstructures are confined by their poor optical properties. To enhance the application potentail of novelty 2D SiO2, we design new hybrid structures of SiO2 and Ag film with the configurations of double-layer SiO2/Ag and triple-layer SiO2/Ag/SiO2. The theoretical calculation shows that the hybrid structures designed by us are stable and perform better than the original SiO2 in the visible region. Besides, the absorption spectrum of the hybrid structures can be modulated by the layer spacing, especially when the layer spacing of the three-layer SiO2/Ag/SiO2 hybrid structure is 3.7 Å ~4.3 Å, the spectrum exhibits double absorption peaks. The results show that the hybrid structures of SiO2 and Ag are valuable candidate material in the fields of photosensitive detectors, thin-film solar cells, and optical switches.

Multifunctional device with an integration of light emitting, photo detective, and energy harvesting

AbstractIn this work, we present a multifunctional device based on a heterojunction active layer formed between the halide perovskite and chalcogenide quantum dots. The device is demonstrated with an integration of proof‐of‐concept functions, including a voltage controllable multicolor light‐emitting diode, an efficient energy harvesting device, and a photosensitive detector. The concept of the heterojunction active layer provides a feasible route to design efficient multifunctional devices in the future.

Machine learning-based multi-modal information perception for soft robotic hands

This paper focuses on multi-modal Information Perception (IP) for Soft Robotic Hands (SRHs) using Machine Learning (ML) algorithms. A flexible Optical Fiber-based Curvature Sensor (OFCS) is fabricated, consisting of a Light-Emitting Diode (LED), photosensitive detector, and optical fiber. Bending the roughened optical fiber generates lower light intensity, which reflecting the curvature of the soft finger. Together with the curvature and pressure information, multi-modal IP is performed to improve the recognition accuracy. Recognitions of gesture, object shape, size, and weight are implemented with multiple ML approaches, including the Supervised Learning Algorithms (SLAs) of K-Nearest Neighbor (KNN), Support Vector Machine (SVM), Logistic Regression (LR), and the unSupervised Learning Algorithm (un-SLA) of K-Means Clustering (KMC). Moreover, Optical Sensor Information (OSI), Pressure Sensor Information (PSI), and Double-Sensor Information (DSI) are adopted to compare the recognition accuracies. The experiment results demonstrate that the proposed sensors and recognition approaches are feasible and effective. The recognition accuracies obtained using the above ML algorithms and three modes of sensor information are higher than 85 percent for almost all combinations. Moreover, DSI is more accurate when compared to single modal sensor information and the KNN algorithm with a DSI outperforms the other combinations in recognition accuracy.

20.3: Multifunctional device with an integration of light emitting, photo detective, and energy harvesting

In this work, we demonstrate a multifunctional device based on a heterojunction between halide perovskite and CdSe chalcogenide quantum dots. The device is an integration of proof‐of‐concept functions, including a voltage controllable multicolor light‐emitting diode, an efficient energy harvesting device, and a photosensitive detector. The heterojunction concept provides a feasible route to design efficient multifunctional devices in the future.

Gaussian mixture models as automated particle classifiers for fast neutron detectors

AbstractPulse shape discrimination (PSD) is the task of classifying electronic pulse shapes for different particle types such as gamma rays and fast neutrons interacting in scintillators and read out by photo sensitive detectors. This field has been limited in its adoption of techniques found in the statistical learning community. Methods initially employed in the 1960s for analog electronic circuitry persist in the current PSD literature describing operations performed on digitized pulses, which are amenable to statistical rigor. Despite vast amounts of data collected at low energy levels, traditional PSD methods are unable to discriminate particles below a certain threshold. In this work, Gaussian mixture models (GMMs) are used as a clustering technique for fast neutron detection in the absence of labeled data. GMMs yield improvements spanning the energy spectrum in a desirably efficient, unsupervised fashion. An extension, the Dirichlet Process GMM, provides further flexibility and classification improvement.

Multifunctional Optoelectronic Device Based on an Asymmetric Active Layer Structure

AbstractA single device with a variety of capabilities is highly attractive for the increasing demands of complex and multifunctional optoelectronics. A hybrid heterojunction formed between CsPbBr3 halide perovskite and chalcogenide quantum dots is demonstrated. The heterojunction served as an asymmetric active layer allows not only charge separation/exciton dissociation in a benign process, but also carrier injection/recombination with the suppression of bulk and interfacial nonradiative recombination. An individual device incorporating such a heterojunction is therefore implemented with an integration of proof‐of‐concept functions, including a voltage controllable multicolor light‐emitting diode, an exceptionally high photovoltage energy‐harvesting device, and an ultrafast photosensitive detector. The figures of merit of the light‐emitting diode remarkably surpass those of the corresponding single‐active‐layer device, particularly in terms of its bright electroluminescence and superior long‐term stability. The asymmetric active layer concept provides a feasible route to design efficient multifunctional and monofunctional devices in the future.

Design of Automatic Fire Alarm System in Workshop of Chemical Plant

With the continuous development and application of new technologies and new products, Chemical plant reconstruction and expansion projects continue to increase. In addition, chemical production itself has flammable, explosive, toxic, harmful, corrosive and other characteristics, the potential risk factors increased, factory fires occur frequently. Therefore, in order to ensure the safety of life and property, a set of convenient automatic fire alarm system is designed for the workshop of chemical plant. Firstly, the system detects abnormal signals from three aspects of temperature sensing detector, smoke detector and photosensitive detector. The measuring signal is then transmitted to the PLC centralized control center via a transmitter, the controller makes a quick decision according to the preset program and sends out the corresponding control signal. If there is a fire, start the automatic fire extinguishing system and smoke exhaust system at the same time as the alarm, finally, the fire is nipped in the bud. The system uses one to many signal docking to facilitate the use of different places, and each detection area system has more than two different alarms to prevent false negatives and false positives. It is not only suitable for the use of a petrochemical factory, but also can be used in schools, warehouses, offices and other places.

A study of the effects of aligned vertically growth time on ZnO nanorods deposited for the first time on Teflon substrate

In this study, ZnO nanorods (NRs) were well deposited on Teflon substrates (PTFE) via a chemical bath deposition (CBD) method at low temperature. The consequences of growth time (1h–4h) on the structural and optical properties of the aligned ZnO (NRs) were investigated through X-ray diffraction, field-emission scanning electron microscopy (FESEM), and photoluminescence (PL) analyses. The results show that the ZnO (NRs) were preferred to grew aligned along the c-axis as hexagonal wurtzite structure as proved by the sharp and strong ZnO (002) peaks of the ZnO (NRs). Irrespective of the growth continuation, FESEM photos confirmed that the ZnO nanorods arrays were fit to be aligned along the c-axis and perpendicular to (PTFE) substrates. The ZnO nanorods that exhibited the sharper stand most intense PL peaks among the sample were grown for 3hs as demonstrated by PL spectra. The device further showed a sensitivity of 4068 to low-power (1.25mW/cm2) 375nm light pulses without an external bias. The measurements of photoresponse demonstrated the highly reproducible characteristics of the fabricated UV detector with rapid response and baseline recovery times of 48.05ms. Thus, this work introduced a simple, low-cost method of fabricating rapid-response, and highly photosensitive UV detectors with zero power consumption on Teflon substrates.

Synthesis of ZnO nanorods by microwave-assisted chemical-bath deposition for highly sensitive self-powered UV detection application

High-quality vertically aligned zinc oxide (ZnO) nanorods were successfully grown on seeded silicon substrates p-Si(100) through microwave-assisted chemical bath deposition. Structural and morphological analyses revealed hexagonal wurtzite nanorods perpendicular to the substrate along the c-axis in the direction of the (002) plane. Optical measurements showed a high-intensity UV peak with a low broad visible peak. UV emission was compared with the visible emission having an IUV/Ivis ratio of 53. A metal–semiconductor–metal-based UV detector was then fabricated by depositing two metal contacts onto the ZnO nanorod surfaces. Current–voltage measurements revealed a highly sensitive device with a self-powered characteristic. At zero applied bias, the fabricated device showed a significant difference between the UV current and dark current. The device further showed a sensitivity of 304×104 to low-power (1.5mW/cm2) 365nm light pulses without an external bias. Photoresponse measurements demonstrated the highly reproducible characteristics of the fabricated UV detector with rapid response and baseline recovery times of 10ms. This work introduced a simple, low-cost method of fabricating rapid-response, highly photosensitive UV detectors with zero power consumption.

Increasing the collection efficiency of time-correlated single-photon counting with single-photon avalanche diodes using immersion lenses.

Single-photon avalanche diodes (SPADs) achieving high timing resolution (≈20-50 ps) developed for time-correlated single-photon counting (TCSPC) generally have very small photosensitive areas (25-100 μm in diameter). This limits the achievable photon counting rate and signal-to-noise ratio and may lead to long counting times. This is detrimental in applications requiring several measurements, such as fluorescence lifetime imaging (FLIM) microscopy, which requires scanning, and time-domain diffuse optical tomography (TD-DOT). We show in this work that the use of an immersion lens directly affixed onto the photosensitive area of the SPAD helps alleviate this problem by allowing more light to be concentrated onto the detector. Following careful optical design and simulations, our experimental results show that it is actually possible to achieve the predicted theoretical increase in the photon counting rate (we achieve a factor of ≈4 here). This work is of high relevance in high timing resolution TCSPC with small photosensitive area detectors and should find widespread interest in FLIM and TD-DOT with SPADs.

A 16-microcantilever array sensing system for the rapid and simultaneous detection of analyte

We report on a new 16 microcantilever sensor system for performing sensing experiments in liquid or gas. The system uses two 8-microcantilever arrays that are held in a sensor cell. The microcantilever deflections are monitored by oscillating two focused optical beams over the microcantilevers such that only one microcantilever is illuminated at one time and each microcantilever is illuminated approximately once per second. The optical beams are moved using a motorized translation stage. The reflected optical beams are detected by a two-axis photo-sensitive detector (PSD) producing a series of two eight peak shaped patterns. The raw data from both the PSD and the translation stage are used to fold the peak shaped patterns from each array one on top of the other so that the deflection of the cantilevers can be obtained from the change in height of each peak. The stability of the data was found to be highly dependent on the speed of the translation stage. When the translation stage was operated between 0.5 and 1mm/s, the deflection of each microcantilever in units of surface stress was found to be highly reproducible and consistent between arrays. As a proof-of-purpose application, the system was used to detect Ca2+, Sr2+ and Cs+ ions using different calix[4]arene-based sensing layers. The results obtained were found to be reproducible and completely consistent with results obtained using a typical two single microcantilever sensor set-up.

On-chip light detection using monolithically integrated quantum dot micropillars

We demonstrate the on-chip detection of light using photosensitive detectors based on quantum dot micropillar cavities. These microscale detectors are applied exemplarily to probe the emission of a monolithically integrated, electrically pumped whispering gallery mode microlaser. Light is detected via the photocurrent induced in the electrically contacted micropillar detectors under reverse-bias. In order to demonstrate the high potential and applicability of the microdetector presented, we determine the threshold current of an integrated microlaser to be (54 ± 4) μA, in very good agreement with the value of (53 ± 4) μA inferred from the optical data. Within this work, we realize the monolithic integration of a laser and a detector in a single device operating in the regime of cavity-quantum electrodynamics. Our results thus advance the research on microscale sensor technology towards the few-photon quantum limit and pave the way for on-chip opto-electronic feedback experiments.

Hierarchical CdS Nanowires Based Rigid and Flexible Photodetectors with Ultrahigh Sensitivity.

Hierarchical CdS nanowires were synthesized via a facile vapor transport method, which were used to fabricate both rigid and flexible visible-light photodetectors. Studies found that the rigid photodetectors on SiO2/Si substrate showed ultrahigh photo-dark current ratio up to 1.96 × 10(4), several orders of magnitude higher than previously reported CdS nanostructures, as well as high specific detectivity (4.27 × 10(12) Jones), fast response speed and excellent environmental stability. Highly flexible photodetectors were also fabricated on polyimide substrate, which exhibited comparable photoresponse performance as the rigid one. In addition, the as-prepared flexible devices displayed excellent mechanical flexibility, electrical stability and folding endurance. The results indicate that the hierarchical CdS nanowires may be good candidates for nanoscale optoelectronic devices such as high-efficiency photoswitches and highly photosensitive detectors.