Photodetector Unit Research Articles

Colorful visualization detection of near-infrared light enabled by an upconversion device with a color-tunable quantum dot light-emitting unit

Color-tunable near-infrared (NIR)-to-visible upconversion devices (UCDs) that correlate the NIR power intensity with the visible emission color are highly desired and hold promise for interactive signal visualization in intelligent optoelectronic devices. In this work, solution-processed color-tunable UCDs integrating a NIR sensing photodetector unit and a color-tunable quantum dot (QD) light-emitting unit are demonstrated. We mixed the red and green QDs in a single emissive layer (EML) for multi-color emission from the UCDs, which is quite different from the previously reported work that used multiple EMLs with different colors. The image color of the resulting color-tunable UCDs can be modulated by bias voltage and driving current and shows a wide color-span range from red to green as the NIR intensity increases. Finally, we present a qualitative correlation between the incident NIR power intensity and the visible emission color, which enables colorful visualization detection of NIR light.

Shortwave Infrared Polarization Imaging and Monolithic Integrated Polarization Amplification Systems Based on Aligned Carbon Nanotube Arrays

AbstractNext‐generation shortwave infrared (SWIR) imaging systems generally require a multidimensional information sensing capability (including intensity, wavelength, polarization, phase, etc.), a highly integrated photodetector unit, and information processing, allowing for miniaturization and low‐cost production. However, traditional polarized SWIR imaging systems with integrated polarizer arrays as supplementary filters and silicon‐based amplifying circuits are complicated and very expensive. Here, a SWIR polarization‐sensitive photodetector and a monolithic integrated polarization amplification system (MIPAS) based on well‐aligned carbon nanotube (CNT) arrays are demonstrated. The polarization‐sensitive CNT photodetector exhibits anisotropic ratios of ≈5.18 and ≈7.56 at 1800 and 2000 nm wavelengths, respectively, and high‐resolution characteristics that can be utilized to image SWIR laser spots with a radius of less than 10 µm. Furthermore, MIPAS including a CNT field‐effect transistor, a CNT loading resistor, and a polarization‐sensitive CNT photodetector is used to increase the anisotropic ratio of the CNT photodetector. The amplified anisotropic ratio is improved up to 173 and 243 at 1800 and 2000 nm wavelengths, respectively, which is the maximum reported in the SWIR band. Our work demonstrates that the CNT polarization‐sensitive photodetector has the potential for SWIR polarization imaging with a monolithic integrated polarization amplification system.

Solar-blind UV communication based on sensitive β -Ga2O3 photoconductive detector array

In this work, a solar-blind UV photodetector array is fabricated and discussed, based on a metalorganic chemical vapor deposition-grown β-Ga2O3 thin film, toward optical communication application. The high-performance photodetector unit shows a significant photo-to-dark current ratio of 3.4 × 105, a high responsivity of 61.3 A/W, an external quantum efficiency of 3 × 104%, a specific detectivity of 5.2 × 1014 Jones, and a fast response time of 35 ms. In addition, a solar-blind UV/visible light rejection ratio of 2.43 × 102 is achieved, suggesting decent spectral selectivity. For the array, the maximum photocurrent standard deviation is below 12% for every group with a similar layout arrangement. Furthermore, the dark current is at picoampere level, leading to low background noise for the optical communication system. Taking the 50% photocurrent value as the readout threshold line to avoid interference from the exterior meanwhile retaining about 500 on/off cycles, the optical communicated result shows effective outputting information “NJUPT2023” coming from a total of 256 “1” and “0” signals.

Stochastic simulation of a signal on a photodetector matrix of a laser navigation system

Abstract Algorithms for stochastic simulation of the signal arriving at the photodetector matrix of the aircraft navigation system are constructed. During the operation of the aircraft landing navigation system, the laser beam of the navigation system coincides in its direction with the glide path determining safe landing. Two photodetector units placed on board of the aircraft determine the glide path position in the coordinate system of the aircraft, which allows one to adjust the position of the touch point on the runway in poor visibility conditions. In this case, the estimation of the power and angular distributions of radiation recorded by the receiver of the navigation system is a relevant problem. In addition, it is interesting to study the effect of scattering of various multiplicities on the recorded signal. The algorithms developed here are based on direct statistical modelling (estimation over collisions) and local estimates of the Monte Carlo method. The calculations show that the proposed methods allow us to evaluate the efficiency of the laser navigation system in various conditions.

Elaborating the interplay between the detecting unit and emitting unit in infrared quantum dot up-conversion photodetectors.

The quantum dot up-conversion device combines an infrared photodetector (PD) and a visible quantum-dot light-emitting diode (QLED) to directly convert infrared targets to visible images. However, large efficiency loss is usually induced by the integration of the detecting unit and the emitting unit. One of the important reasons is the performances of the PD and QLED units restraining each other. We regulated the equilibrium between infrared absorption and visible emission by changing the thicknesses of infrared active layers in up-conversion devices. A good balance could be achieved between the absorption of 980 nm incident light and the out-coupling of the 634 nm emission when the active layer thickness is 140 nm, leading to the best performance of the up-conversion device. As more photogenerated carriers are produced with the increase of infrared illumination intensity, the external quantum efficiency (EQE) of the QLED unit in the up-conversion device remains little changed. This suggests the limited amount of photogenerated holes in the PD unit does not limit the EQE of the QLED unit. However, a PD unit with a high ratio of photogenerated holes trapped near the interconnection decreased the EQE in the QLED unit. This work provides new insights into the interplay between the PD and QLED units in up-conversion devices, which is crucial for their further improvements.

Coordinate measurement in multi-beam drone positioning system

The multi beam drone positioning system for automatic measurements of drone coordinates is presented. One part of this system is installed round a landing pad or a goods delivery pad. It forms a set of low-energy optical beams of definite shapes in three-dimensional space. Each beam transmits a digital code that characterizes its location relatively this pad. Second part of this system is a small set of miniature photodetector units that are fixed under a drone. The paper describes the technique based of the beam code analysis for calculation of drone coordinates relatively a landing pad. This system guarantees the accuracy that is necessary for accurate drone taking off, landing or goods delivery without usage of an expensive digital camera or a human operator. The advantages and possible applications of these sensors are also discussed.

A High-Performance ε-Ga2O3-Based Deep-Ultraviolet Photodetector Array for Solar-Blind Imaging.

One of the most important applications of photodetectors is as sensing units in imaging systems. In practical applications, a photodetector array with high uniformity and high performance is an indispensable part of the imaging system. Herein, a photodetector array (5 × 4) consisting of 20 photodetector units, in which the photosensitive layer involves preprocessing commercial ε-Ga2O3 films with high temperature annealing, have been constructed by low-cost magnetron sputtering and mask processes. The ε-Ga2O3 ultraviolet photodetector unit shows excellent responsivity and detectivity of 6.18 A/W and 5 × 1013 Jones, respectively, an ultra-high light-to-dark ratio of 1.45 × 105, and a fast photoresponse speed (0.14/0.09 s). At the same time, the device also shows good solar-blind characteristics and stability. Based on this, we demonstrate an ε-Ga2O3-thin-film-based solar-blind ultraviolet detector array with high uniformity and high performance for solar-blind imaging in optoelectronic integration applications.

Method for measuring the relative phases among the three beams in the case of homodyne three-beam interference

A method for measuring the relative phases (RPs) among the three beams in the case of homodyne three-beam interference (TBI) is proposed and verified by the ZEMAX simulation in this paper. The method requires that the interference beams are not on the same plane, that is, any two of the three beams interfere at an angle in different planes. Based on the phase delay of the beam in space, the inclined beams have different phases at different positions within the beams' range. By arranging the photodetector array within the interference area, the RPs can be calculated using the intensity of the interference light received by specific photodetector units. The application of the algorithm for the displacement measurement of the homodyne three-beam interferometer (TBIR) has been verified by simulation. The beam number of three-beam interference is one less than that of two two-beam interference when measuring two relative phases. Compared with the two-beam interferometer, the TBIR applied to two-degree-of-freedom displacement measurement is more compact in structure due to the more compact phase measurement components.

Monte Carlo simulation driven time resolved photon fluence analysis

In this study, time resolved (TR) Monte Carlo (MC) simulation program code was run to generate photon fluencies with increasing time steps. TR MC simulation was performed for ten time series from 4 ps to 52 ps. Generated photon fluencies were transferred to the image analysis programming platform. Imaging device geometry was created for test purpose in image reconstruction programming platform environment. Forward model weight matrix functions were calculated during each time period for 38 sources, and 38 detectors according to the back-reflected imaging geometry. A homogenous phantom, which simulated tissue, was chosen. Depending on the homogeneous tissue optical properties, such as tissue absorption coefficient μa, and tissue scattering coefficient μs, photons emitted from the laser source positions; migrated differently inside the imaging tissue. Photons migrate inside the tissue by some multiplication factor of ps depending on the tissue type for each 100-micrometer vertical distance. Superficial photons come photodetector point fast, depend on the source-detector neighborhood distances and tissue optical properties, respectively. Time resolved diffuse optic tomography (TRDOT) imaging systems are an emerging biomedical optic imaging modality due to progressive electronic technologies are helping to build the systems faster and cheap. As such, emerging microelectronic technology is giving important access to design and implement compact laser sources and photodetector units. Vertical cavity surface emitting light (VCSEL) as laser source and single photon avalanche diode (SPAD) arrays as photodetector units are becoming in common use as important hardware tools for designers and researchers in this field. TR diffuse photon analysis should be done routinely for better understanding of TRDOT devices. Hence, MC simulation driven TR photon fluence analysis was done for such a purpose in this study.

High-power traveling-wave photodetector based on an aperiodically loaded open-circuit electrode.

We demonstrate a four-stage silicon distributed traveling-wave photodetector (TWPD) whose input terminal is open-circuit so as to enhance the radio-frequency (RF) output power. In order to mitigate the bandwidth drop caused by the RF reflection at the open input terminal, photodetector (PD) units are aperiodically loaded on the TW electrode. With the aid of an equivalent circuit model, we optimize spacings between PD units and then improve the 3dB bandwidth from 7 to 10GHz. A good agreement between measurement and modeling is obtained. Thanks to the cancellation of the input termination impedance, maximum RF output powers of the device are 10.2 and 6.5dBm at 5 and 10GHz, respectively. The corresponding power conversion efficiencies are 7.0% and 3.2%.

Nanosecond-Response Speed Sensor Based on Perovskite Single Crystal Photodetector Array

A nanosecond-response speed sensor is demonstrated based on a CH3NH3PbI3 perovskite single crystal photodetector array. The responsivity of the CH3NH3PbI3 photodetector unit is as high as 1.55 × 102 A/W under 1.93 × 10–2 mW/cm2 illumination with a 532 nm laser. The ultrafast response time of less than 12.5 ns makes it possible for ultra-high-speed detection. Owing to the uniformity of as-prepared CH3NH3PbI3 single crystals, each array element shows a consistent performance. When a shelter moves across the photodetector array, the time delay of the photoresponses between two neighboring array elements can be recorded promptly. Therefore, the speed of the moving shelter can be calculated easily. Besides speed sensing, the ability to capture the trajectory of a moving object is also demonstrated. The nanosecond-response speed sensor presented here demonstrates great potential for applying in high-speed detection.

A Silicon Aperiodically Distributed Traveling-Wave Photodetector With Enhanced RF Output Power

We propose an aperiodic loading technique to enhance the RF output power of a silicon distributed traveling-wave photodetector (TWPD), which can be used to handle high optical powers in analog optical links. This technique contains a traveling wave electrode whose input terminal is open circuit so as to avoid shunting any photocurrent from the photodetector (PD) array. As a result, the RF output to the load impedance that locates at the other terminal is enhanced. To mitigate the bandwidth reduction caused by the strong RF reflection at the open input terminal, the spacing between adjacent PD units gradually increases from the input to the load terminals. By breaking the balanced distribution of the photocurrent from each PD among the forward and the backward propagation directions, this arrangement weakens the strength of the interference between the forward and the reflected backward RF waves, and hence improves the bandwidth. In order to validate this operation principle, an analytical model is developed to calculate the frequency response of the silicon distributed TWPD. The model then is used to optimize both periodically and aperiodically distributed TWPDs on silicon. After the optimization, the 3-dB bandwidth of a four-stage aperiodic TWPD is 25.7 GHz, which is only 0.8 GHz lower than that of a four-stage periodic TWPD. However, since the aperiodic TWPD eliminates the matching impedance at its input terminal, its RF output power on the load is four times as strong as that of the periodic TWPD from 1 to 24.7 GHz.

A pair of integrated optoelectronic transceiving chips for optical interconnects

In this Letter, a pair of integrated optoelectronic transceiving chips is proposed. They are constructed by integrating a vertical cavity surface emitting laser unit above a positive-intrinsic-negative photodetector unit. One of the transceiving chips emits light at the wavelength of 848.1 nm with a threshold current of 0.8 mA and a slope efficiency of 0.81 W/A. It receives light between 801 and 814 nm with a quantum efficiency of higher than 70%. On its counterpart, the other one of the transceiving chips emits light at the wavelength of 805.3 nm with a threshold current of 1.1 mA and a slope efficiency of 0.86 W/A. It receives light between 838 and 855 nm with a quantum efficiency of higher than 70%. The proposed pair of integrated optoelectronic transceiving chips can work full-duplex with each other, and they can be applied to single fiber bidirectional optical interconnects.

PbS quantum dots based organic-inorganic hybrid infrared detecting and display devices

In this letter, we present a new organic-inorganic hybrid infrared detecting & display devices (IR-DDDs), in which a high-efficiency phosphorescent organic light-emitting diode (OLED) as the display unit was integrated directly onto a lead sulfide (PbS) quantum dot based IR photodetector as the detecting unit. When an 850nm IR light incomes to excite the IR-DDD ITO/ZnO/PbS:P3HT:PCBM/Ir(ppy)3:CBP/BCP/Al, a green light emission (peak at 510nm) from Ir(ppy)3:CBP can be observed, and the emission intensity can be controlled by the incident IR illumination and the applied voltage on the IR-DDD. Comparing with OLED ITO/PEDOT:PSS/Ir(ppy)3:CBP/BCP/Al, the influence factors on device performance were investigated and it is mainly determined by the active layer of IR photodetector unit and the electron-transporting layer of the OLED unit.

PHOTODETECTING UNIT OF FBA-210 ASTROPHOMETER WITH A SIMPLE DATA CONVERSION RESPONSE EQUALIZER

A photodetector unit of astrophotometer is reviewed. This device operates in photon counting mode, wherein for the purpose of increasing its conversion linearity characteristics, a linearity equalizer is introduced. The results of experimental research of FDU with the proposed linearity equalizer are included.

The design of a photodetector unit of a new Shashlyk EM calorimeter for COMPASS II

A nine-channel photodetector unit with micropixel avalanche photodiodes (MAPD) and precision thermostabilization based on the compact Peltier module is designed and constructed. MAPD-3N with a high pixel density of 15,000 per square mm and area 3×3mm2 produced by Zecotek were used.

Experimental Evaluation of a SiPM-Based Scintillation Detector for MR-Compatible SPECT Systems

In the present work we briefly describe the architecture of a photo-detection module, designed in the framework of the INSERT (INtegrated SPECT/MRI for Enhanced Stratification in Radio-chemoTherapy) project, supported by the European Community. We focus on two main elements of the module: the SiPM photo-detector unit and the multi-channel ASIC. These two components have been investigated with dedicated and independent setups to assess preliminary performance of INSERT architecture. In details, we designed a $ 25.30~\hbox{mm} \times 25.85~\hbox{mm} $ tile, comprising 9 pixels, each one with an $8~\hbox{mm} \times 8~\hbox{mm}$ active area. We developed an Anger camera to characterize the tile coupled to a CsI:Tl scintillator (6 mm thick). We measured an average spatial resolution (FWHM) of 2 mm in the central region of the Field of View and a 15.3% energy resolution using a $^{57}{\rm Co}$ source (122 keV), when the tile is cooled down to 0 $^ \circ {\rm C }$ to reduce the impact of the dark count rate. Furthermore, we developed ANGUS, a 36-channels $0.35 ~\mu \hbox{m}$ CMOS technology ASIC designed to cope with input capacitance up to 5 nF, typical of large area SiPM pixels. The spectroscopic capability of single readout channels were evaluated by coupling an $8~\hbox{mm} \times 8~\hbox{mm} $ pixel with a cylindrical CsI:Tl scintillator (8 mm diameter, 10 mm thickness). Energy resolution at room temperature provided values between 13% and 13.5% (FWHM) at the 122 keV line for the nine pixels.

Shashlyk EM calorimeter prototype readout by MAPD with superhigh pixel density for COMPASS II

The new-generation high-granularity Shashlyk EM calorimeter readout by micropixel avalanche photodiodes (MAPD) with precision thermostabilization based on the Peltier element is designed, constructed end tested. MAPD-3N with superhigh pixel density 1.5×104mm−2 and area 3×3mm2 manufactured by the Zecotek Company were used in the photodetector unit.

Dual instrument for in vivo and ex vivo OCT imaging in an ENT department

A dual instrument is assembled to investigate the usefulness of optical coherence tomography (OCT) imaging in an ear, nose and throat (ENT) department. Instrument 1 is dedicated to in vivo laryngeal investigation, based on an endoscope probe head assembled by compounding a miniature transversal flying spot scanning probe with a commercial fiber bundle endoscope. This dual probe head is used to implement a dual channel nasolaryngeal endoscopy-OCT system. The two probe heads are used to provide simultaneously OCT cross section images and en face fiber bundle endoscopic images. Instrument 2 is dedicated to either in vivo imaging of accessible surface skin and mucosal lesions of the scalp, face, neck and oral cavity or ex vivo imaging of the same excised tissues, based on a single OCT channel. This uses a better interface optics in a hand held probe. The two instruments share sequentially, the swept source at 1300 nm, the photo-detector unit and the imaging PC. An aiming red laser is permanently connected to the two instruments. This projects visible light collinearly with the 1300 nm beam and allows pixel correspondence between the en face endoscopy image and the cross section OCT image in Instrument 1, as well as surface guidance in Instrument 2 for the operator. The dual channel instrument was initially tested on phantom models and then on patients with suspect laryngeal lesions in a busy ENT practice. This feasibility study demonstrates the OCT potential of the dual imaging instrument as a useful tool in the testing and translation of OCT technology from the lab to the clinic. Instrument 1 is under investigation as a possible endoscopic screening tool for early laryngeal cancer. Larger size and better quality cross-section OCT images produced by Instrument 2 provide a reference base for comparison and continuing research on imaging freshly excised tissue, as well as in vivo interrogation of more superficial skin and mucosal lesions in the head and neck patient.

Improved Efficiency of Organic/Inorganic Hybrid Near-Infrared Light Upconverter by Device Optimization

An organic/inorganic hybrid up-conversion device was demonstrated in this work, which can convert near-infrared light (NIR) to visible green at high conversion efficiency. The upconverter was fabricated by integrating an In(0.12)Ga(0.88)As/GaAs multiquantum wells (MQWs) photodetector (PD) with an organic light emitting diode (OLED). The up-conversion efficiency of 4.0 W/W % was obtained at 20 V under NIR illumination of 1 mW/mm(2) at room temperature by optimizing the structure of the PD unit and adding MoO(3) doped perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as interfacial layer of OLED. Meanwhile, the green light output induced by NIR achieved 6050 cd/m(2), which proves that the organic/inorganic hybrid upconverter an excellent candidate that can be applied in light converter field.