Search Results (89)

Laser ranging technology holds a key position in the military, aerospace, and industrial fields due to its high precision and non-contact measurement characteristics. As a core component, the performance of the photon detector directly determines the ranging accuracy and range. This paper systematically reviews the technological development of photonic detectors for laser ranging, with a focus on analyzing the working principles and performance differences of traditional photodiodes [PN (P-N junction photodiode), PIN (P-intrinsic-N photodiode), and APD (avalanche photodiode)] (such as the high-frequency response characteristics of PIN and the internal gain mechanism of APD), as well as their applications in short- and medium-range scenarios. Additionally, this paper discusses the unique advantages of special structures such as transmitting junction-type and Schottky-type detectors in applications like ultraviolet light detection. This article focuses on photon counting technology, reviewing the technological evolution of photomultiplier tubes (PMTs), single-photon avalanche diodes (SPADs), and superconducting nanowire single-photon detectors (SNSPDs). PMT achieves single-photon detection based on the external photoelectric effect but is limited by volume and anti-interference capability. SPAD achieves sub-decimeter accuracy in 100 km lidars through Geiger mode avalanche doubling, but it faces challenges in dark counting and temperature control. SNSPD, relying on the characteristics of superconducting materials, achieves a detection efficiency of 95% and a dark count rate of less than 1 cps in the 1550 nm band. It has been successfully applied in cutting-edge fields such as 3000 km satellite ranging (with an accuracy of 8 mm) and has broken through the near-infrared bottleneck. This study compares the differences among various detectors in core indicators such as ranging error and spectral response, and looks forward to the future technical paths aimed at improving the resolution of photon numbers and expanding the full-spectrum detection capabilities. It points out that the new generation of detectors represented by SNSPD, through material and process innovations, is promoting laser ranging to leap towards longer distances, higher precision, and wider spectral bands. It has significant application potential in fields such as space debris monitoring. Full article

High-resolution 3D visualization of dynamic environments is critical for applications such as remote sensing. Traditional 3D imaging systems, such as lidar, rely on avalanche photodiode (APD) arrays to determine the flight time of light for each scene pixel. In this context, we introduce and demonstrate a high-resolution 3D imaging approach leveraging an Electron Multiplying Charge Coupled Device (EMCCD). This sensor’s low bandwidth properties allow for the use of electro-optic modulators to achieve both temporal resolution and rapid shuttering at sub-nanosecond speeds. This enables range-gated 3D imaging, which significantly enhances the signal-to-noise ratio (SNR) within our proposed framework. By employing a dual EMCCD setup, it is possible to reconstruct both a depth image and a grayscale image from a single raw data frame, thereby improving dynamic imaging capabilities, irrespective of object or platform movement. Additionally, the adaptive gate-opening range technology can further refine the range resolution of specific scene objects to as low as 10 cm. Full article

This paper presents a CMOS-based optoelectronic receiver integrated circuit (CORIC) realized in a standard 180 nm CMOS technology for the applications of short-distance optical interconnects. The CORIC comprises a spatially modulated P⁺/N-well on-chip avalanche photodiode (P⁺/NW APD) for optical-to-electrical conversion, a dummy APD at the differential input for enhanced common-mode noise rejection, a cross-coupled differential transimpedance amplifier (CCD-TIA) for current-to-voltage conversion, a 3-bit continuous-time linear equalizer (CTLE) for adaptive equalization by using NMOS registers, and a $f_T$-doubler output buffer (OB). The CTLE and $f_T$-doubler OB combination not only compensates the frequency-dependent signal loss, but also provides symmetric differential output signals. Post-layout simulations of the proposed CORIC reveal a transimpedance gain of 53.2 dBΩ, a bandwidth of 4.83 GHz even with a 490 fF parasitic capacitance from the on-chip P⁺/NW APD, a dynamic range of 60 dB that handles the input photocurrents from 1 μA_pp to 1 mA_pp, and a DC power consumption of 33.7 mW from a 1.8 V supply. The CORIC chip core occupies an area of 260 × 101 μm². Full article

Optical communication is a critical technology for future deep space exploration, offering substantial advantages in transmission capacity and spectrum utilization. This paper establishes a comprehensive theoretical framework for avalanche photodiode (APD)-based deep space optical uplink communication under combined channel impairments, including atmospheric and coronal turbulence induced beam scintillation, pointing errors, angle-of-arrival (AOA) fluctuations, link attenuation, and background noise. A closed-form analytical channel model unifying these effects is derived and validated through Monte Carlo simulations. Webb and Gaussian approximations are employed to characterize APD output statistics, with theoretical symbol error rate (SER) expressions for pulse position modulation (PPM) derived under diverse impairment scenarios. Numerical results demonstrate that the Webb model achieves higher accuracy by capturing APD gain dynamics, while the Gaussian approximation remains viable when APD gain exceeds a channel fading-dependent gain threshold. Key system parameters such as APD gain and field-of-view (FOV) angle are analyzed. The optimal APD gain significantly influences the achievement of optimal SER performance, and angle of FOV design balances AOA fluctuations tolerance against noise suppression. These findings enable hardware optimization under size, weight, power, and cost (SWaP-C) constraints without compromising performance. Our work provides critical guidelines for designing robust APD-based deep space optical uplink communication systems. Full article

Laser ranging is a high-precision geodetic technique that plays an indispensable role in the field of geodynamics. Avalanche photodiodes (APDs) offer a series of advantages over other photodetector technologies, including photomultiplier tubes (PMTs) and superconducting single-photon detectors (SNSPDs). These advantages include high sensitivity, small size, high integration, and low power consumption, which have contributed to the widespread use of APDs in laser ranging applications. This paper analyses the key role of APDs in enhancing the accuracy and stability of laser ranging through the examination of application examples, including Si-APD and InGaAs/InP APD. Finally, based on the technological needs of laser ranging, the future development directions of APDs are envisioned, aiming to provide a reference for the research of photodetectors in high-precision and high-frequency laser ranging applications. Full article

This paper presents a theoretical analysis of npBp infrared (IR) barrier avalanche photodiode (APD) performance operating at 300 K based on a quaternary compound made of A^IIIB^V—InGaAsSb, lattice-matched to the GaSb substrate with a p-type barrier made of a ternary compound AlGaSb. Impact ionization in the multiplication layer of InGaAsSb separate absorption, grading, charge, and multiplication avalanche photodiodes (SAGCM APDs) was studied using the Crosslight Software simulation package APSYS. The band structure of the avalanche detector and the electric field distribution for the multiplication and absorption layers were determined. The influence of the multiplication and charge layer parameters on the impact multiplication gain and the excess noise factor was analyzed. It has been shown that with the decrease in the charge layer doping level, the gain and the breakdown voltage increase, but the punch-through voltage decreases, and the linear range of the APD operating voltages widens. The multiplication layer doping level slightly affects the detector parameters, while increasing its width, the photocurrent and the breakdown voltage also increase. The detector structure proposed in this work allows us to obtain a comparable gain and lower dark currents to the APD detectors made of InGaAsSb previously presented in the literature. The performed simulations confirmed the possibility of obtaining APDs with high performance at room temperatures made of InGaAsSb for the SWIR range. Full article

This study explores the impact of a dual-charge layer structure on the performance of InGaAs/InAlAs avalanche photodiodes (APDs) with a separate absorption, charge, multiplication, charge, and transit (SACMCT) structure. The dual-charge layer, consisting of p-doped and n-doped charge layers on either side of the avalanche layer, is designed to precisely control the internal electric field, effectively reduce the dark current, and extend the dynamic range. Simulation results guided the fabrication of a backside-illuminated APD, which achieved a linear operating range of 10–30 V and a dark current as low as 80 nA. The optimized design significantly reduced the dark current and increased the breakdown voltage compared to previously reported APDs. These improvements demonstrate the potential of dual-charge-layer APDs for high-speed optical communications and precision photodetection applications. Full article

In order to meet the reliability requirements of communication for underwater resource exploration, this study develops an underwater wireless optical communication (UWOC) system utilizing a blue semiconductor laser as the light source. At the receiver, a fully digital automatic gain control (AGC) module, implemented on a field-programmable gate array (FPGA), is designed to mitigate signal fluctuations induced by underwater turbulence. Digital filtering techniques, including median filtering (MF) and bilateral edge detection filtering (BEDF), are also employed to improve signal demodulation reliability. An improved Reed–Solomon (RS) coding scheme is further adopted to significantly reduce the bit error rate (BER). The design of a highly reliable UWOC system was realized based on the above techniques. The system’s performance was evaluated across a range of signal-to-noise ratios (SNRs) and bubble intensities. The results show that the digital AGC module can provide a gain range from −3.2 dB to 16 dB, adapting to varying signal strengths, which greatly bolsters the system’s resilience against underwater turbulence. Filtering techniques and RS coding further enhance the system’s immunity to interference and reduce the system BER. Communication experiments were conducted over various distances under three distinct water quality conditions. The results demonstrate that, within the detection range of the avalanche photodiode (APD), the system consistently maintained a BER below 3.8 × 10⁻³ across all water types, thereby confirming its high reliability. In clear seawater, the system demonstrated reliable information transmission over a 10 m distance at a data rate of 10 Mbps, achieving a BER of 2 × 10⁻⁸. Theoretical calculations indicate that the maximum transmission distance in clear seawater can reach 111.35 m. Full article

This paper presents two novel avalanche photodiode (APD) array structures designed to significantly enhance both detection area and bandwidth, overcoming the common trade-off between these parameters in conventional photodetectors. The impact of various parameters on the bandwidths of the two distinct array structures was theoretically simulated. Experimental validation using the self-fabricated 2 × 2 array on PCB board confirmed the bandwidth enhancement realized through inductor integration, with one APD array demonstrating an increase to 780 MHz (1.41 times greater) and another showing an increase to 1.21 GHz (1.35 times greater). Unlike prior works where array bandwidth is often lower than single detectors, our structures maintain high bandwidth while expanding the detection area. Structure 2 is particularly recommended over Structure 1 because of its lower noise, better signal-to-noise ratio (SNR), and reduced power consumption. Full article

The Geiger-Mode Avalanche Photodiode (Gm-APD) LiDAR system demonstrates high-precision detection capabilities over long distances. However, the detection of occluded small objects at long distances poses significant challenges, limiting its practical application. To address this issue, we propose a multi-scale spatio-temporal object detection network (MSTOD-Net), designed to associate object information across different spatio-temporal scales for the effective detection of occluded small objects. Specifically, in the encoding stage, a dual-channel feature fusion framework is employed to process range and intensity images from consecutive time frames, facilitating the detection of occluded objects. Considering the significant differences between range and intensity images, a multi-scale context-aware (MSCA) module and a feature fusion (FF) module are incorporated to enable efficient cross-scale feature interaction and enhance small object detection. Additionally, an edge perception (EDGP) module is integrated into the network’s shallow layers to refine the edge details and enhance the information in unoccluded regions. In the decoding stage, feature maps from the encoder are upsampled and combined with multi-level fused features, and four prediction heads are employed to decode the object categories, confidence, widths and heights, and displacement offsets. The experimental results demonstrate that the MSTOD-Net achieves mAP₅₀ and mAR₅₀ scores of 96.4% and 96.9%, respectively, outperforming the state-of-the-art methods. Full article

Photodetectors with broad spectral response and high responsivity demonstrate significant potential in optoelectronic applications. This study proposes a Si/Ge avalanche photodiode featuring nanostructures that enhance light absorption. By optimizing the device epitaxial structure and these nanostructures, a wide spectral responsivity from 0.4 to 1.6 μm is achieved. The results demonstrate that introducing surface photon-trapping nanoholes and SiO₂ reflective grating nanostructures increases the average light absorptivity from 0.64 to 0.84 in the 0.4–1.1 μm range and from 0.31 to 0.56 in the 1.1–1.6 μm range. At an applied bias of 0.95 V_br-apd, the responsivity reaches 17.24 A/W at 1.31 μm and 17.6 A/W at 1.55 μm. This research provides theoretical insights for designing high-responsivity photodetectors in the visible–near-infrared broadband spectrum. Full article

This paper introduces an analog differential optoelectronic receiver (ADOR) integrated with digital slicers for short-range LiDAR systems, consisting of a spatially modulated P⁺/N-well on-chip avalanche photodiode (APD), a cross-coupled differential transimpedance amplifier (CCD-TIA) with cross-coupled active loads, a continuous-time linear equalizer (CTLE), a limiting amplifier (LA), and dual digital slicers. A key feature is the integration of an additional on-chip dummy APD at the differential input node, which enables the proposed ADOR to outperform a traditional single-ended TIA in terms of common-mode noise rejection ratio. Also, the CCD-TIA utilizes cross-coupled PMOS-NMOS active loads not only to generate the symmetric output waveforms with maximized voltage swings, but also to provide wide bandwidth characteristics. The following CTLE extends the receiver bandwidth further, allowing the dual digital slicers to operate efficiently even at high sampling rates. The LA boosts the output amplitudes to suitable levels for the following slicers. Then, the inverter-based slicers with low power consumption and a small chip area produce digital outputs. The fabricated ADOR chip using a 180 nm CMOS process demonstrates a 20 dB dynamic range from 100 μA_pp to 1 mA_pp, 2 Gb/s data rate with a 490 fF APD capacitance, and 22.7 mW power consumption from a 1.8 V supply. Full article

Array Geiger-mode avalanche photodiode (GM-APD) Light Detection and Ranging (LiDAR) has the advantages of high sensitivity and long imaging range. However, due to its operating principle, GM-APD LiDAR requires processing based on multiple-laser-pulse data to complete the target reconstruction. Therefore, the influence of the device’s movement or scanning motion during GM-APD LiDAR imaging cannot be ignored. To solve this problem, we designed a reconstruction method based on coordinate system transformation and the Position and Orientation System (POS). The position, attitude, and scanning angles provided by POS and angular encoders are used to reduce or eliminate the dynamic effects in multiple-laser-pulse detection. Then, an optimization equation is constructed based on the negative-binomial distribution detection model of GM-APD. The spatial distribution of photons in the scene is ultimately computed. This method avoids the need for field-of-view registration, improves data utilization, and reduces the complexity of the algorithm while eliminating the effect of LiDAR motion. Moreover, with sufficient data acquisition, this method can achieve super-resolution reconstruction. Finally, numerical simulations and imaging experiments verify the effectiveness of the proposed method. For a 1.95 km building scene with SBR ~0.137, the 2 × 2-fold super-resolution reconstruction results obtained by this method reduce the distance error by an order of magnitude compared to traditional methods. Full article

In this paper, a CMOS optoelectronic analog front-end (AFE) preamplifier with cross-coupled active loads for short range LiDAR applications is presented, which consists of a spatially modulated P⁺/N-well on-chip avalanche photodiode (APD), the differential input stage with cross-coupled active loads, and an output buffer. Particularly, another on-chip dummy APD is inserted at the differential input node to improve the common-mode noise rejection ratio significantly better than conventional single-ended TIAs. Moreover, the cross-coupled active loads are exploited at the output nodes of the preamplifier not only to help generate symmetric output waveforms, but also to enable the limiting operations even without the following post-amplifiers. In addition, the inductive behavior of the cross-coupled active loads extends the bandwidth further. The proposed AFE preamplifier implemented in a 180-nm CMOS process demonstrate the measured results of 63.5 dB dynamic range (i.e., 1 µA_pp~1.5 mA_pp input current recovery), 67.8 dBΩ transimpedance gain, 1.6 GHz bandwidth for the APD capacitance of 490 fF, 6.83 pA⁄√Hz noise current spectral density, 85 dB power supply rejection ratio, and 32.4 mW power dissipation from a single 1.8 V supply. The chip core occupies the area of 206 × 150 µm². Full article

This paper presents a low-noise CMOS transimpedance-limiting amplifier (CTLA) for application in LiDAR sensor systems. The proposed CTLA employs a dual-feedback architecture that combines the passive and active feedback mechanisms simultaneously, thereby enabling automatic limiting operations for input photocurrents exceeding 100 µA_pp (up to 1.06 mA_pp) without introducing signal distortions. This design methodology can eliminate the need for a power-hungry multi-stage limiting amplifier, hence significantly improving the power efficiency of LiDAR sensors. The practical implementation for this purpose is to insert a simple NMOS switch between the on-chip avalanche photodiode (APD) and the active feedback amplifier, which then can provide automatic on/off switching in response to variations of the input currents. In particular, the feedback resistor in the active feedback path should be carefully optimized to guarantee the circuit’s robustness and stability. To validate its practicality, the proposed CTLA chips were fabricated in a 180 nm CMOS process, demonstrating a transimpedance gain of 88.8 dBΩ, a −3 dB bandwidth of 629 MHz, a noise current spectral density of 2.31 pA/√Hz, an input dynamic range of 56.6 dB, and a power dissipation of 23.6 mW from a single 1.8 V supply. The chip core was realized within a compact area of 180 × 50 µm². The proposed CTLA shows a potential solution that is well-suited for power-efficient LiDAR sensor systems in real-world scenarios. Full article