Compact CMOS active quenching/recharge circuit for SPAD arrays

Avalanche diodes operating in Geiger mode are able to detect single photon events. They can be employed to photon counting and time‐of‐flight estimation. In order to ensure proper operation of these devices, the avalanche current must be rapidly quenched, and, later on, the initial equilibrium must be restored. In this paper, we present an active quenching/recharge circuit specially designed to be integrated in the form of an array of single‐photon avalanche diode (SPAD) detectors. Active quenching and recharge provide benefits like an accurately controllable pulse width and afterpulsing reduction. In addition, this circuit yields one of the lowest reported area occupations and power consumptions. The quenching mechanism employed is based on a positive feedback loop that accelerates quenching right after sensing the avalanche current. We have employed a current starved inverter for the regulation of the hold‐off time, which is more compact than other reported controllable delay implementations. This circuit has been fabricated in a standard 0.18 µm complementary metal‐oxide‐semiconductor (CMOS) technology. The SPAD has a quasi‐circular shape of 12 µm diameter active area. The fill factor is about 11%. The measured time resolution of the detector is 187 ps. The photon‐detection efficiency (PDE) at 540 nm wavelength is about 5% at an excess voltage of 900 mV. The break‐down voltage is 10.3 V. A dark count rate of 19 kHz is measured at room temperature. Worst case post‐layout simulations show a 117 ps quenching and 280 ps restoring times. The dead time can be accurately tuned from 5 to 500 ns. The pulse‐width jitter is below 1.8 ns when dead time is set to 40 ns. Copyright © 2015 John Wiley & Sons, Ltd.     

Arrays of InP-based Avalanche Photodiodes for Photon Counting

Arrays of InP-based avalanche photodiodes (APDs) with InGaAsP absorber regions have been fabricated and characterized in the Geiger mode for photon-counting applications. Measurements of APDs with InGaAsP absorbers optimized for 1.06 mum wavelength show dark count rates (DCRs) <20 kHz for room-temperature operation with photon detection efficiency (PDE) up to 50% and a reset or dead time of 1s. APDs with InGaAs absorbers optimized for 1.55 mum wavelength and 240 K temperature have DCRs <20 kHz, PDE up to 45%, and a reset time of ~6 mus. Arrays for both wavelengths have been fabricated and packaged with GaP microlenses (of 100 and 50 mum pitch) and CMOS readout integrated circuits (ROICs). Comparisons are made between ROICs that operate in the framed-readout mode as well as those that operate in continuous-readout mode.     

Single-Photon Detection System for Quantum Optics Applications

We describe the design and characterization of a fiber-coupled double-channel single-photon detection system based on superconducting single-photon detectors (SSPD), and its application for quantum optics experiments on semiconductor nanostructures. When operated at 2-K temperature, the system shows 10% quantum efficiency at 1.3-mum wavelength with dark count rate below 10 counts per second and timing resolution <100 ps. The short recovery time and absence of afterpulsing leads to counting frequencies as high as 40 MHz. Moreover, the low dark count rate allows operation in continuous mode (without gating). These characteristics are very attractive-as compared to InGaAs avalanche photodiodes-for quantum optics experiments at telecommunication wavelengths. We demonstrate the use of the system in time-correlated fluorescence spectroscopy of quantum wells and in the measurement of the intensity correlation function of light emitted by semiconductor quantum dots at 1300 nm.     

High-Performance InGaAs/InP Single-Photon Avalanche Photodiode

In_0.53Ga_0.47As/InP avalanche photodiodes with very low dark current have been characterized in gated mode for single-photon detection. A 40-mum-diameter single-photon avalanche diodes (SPAD) exhibited high single-photon detection efficiency (SPDE = 45% at 1.31 mum), low dark count rate (DCR = 12 kHz), and low noise-equivalent power (NEP=4.5X 10^-17W/Hz^1/2 W/Hz) at 200 K and 1.31 mum. A timing resolution of 140 ps was achieved with an SPDE of 45%. In addition, the dark current and DCR of a 4X4 SPAD array are reported.     

Progress in Silicon Single-Photon Avalanche Diodes

Silicon single-photon avalanche diodes (SPADs) are nowadays a solid-state alternative to photomultiplier tubes (PMTs) in single-photon counting (SPC) and time-correlated single-photon counting (TCSPC) over the visible spectral range up to 1-mum wavelength. SPADs implemented in planar technology compatible with CMOS circuits offer typical advantages of microelectronic devices (small size, ruggedness, low voltage, low power, etc.). Furthermore, they have inherently higher photon detection efficiency, since they do not rely on electron emission in vacuum from a photocathode as do PMTs, but instead on the internal photoelectric effect. However, PMTs offer much wider sensitive area, which greatly simplifies the design of optical systems; they also attain remarkable performance at high counting rate, and offer picosecond timing resolution with microchannel plate models. In order to make SPAD detectors more competitive in a broader range of SPC and TCSPC applications, it is necessary to face several issues in the semiconductor device design and technology. Such issues will be discussed in the context of the two possible approaches to such a challenge: employing a standard industrial high-voltage CMOS technology or developing a dedicated CMOS-compatible technology. Advances recently attained in the development of SPAD detectors will be outlined and discussed with reference to both single-element detectors and integrated detector arrays.     

Photon-timing detector module for single-molecule spectroscopy with 60-ps resolution

Advanced fluorescence measurements on single molecules demand single-photon detectors with high-quantum detection efficiency, low noise, and high time resolution. We have developed a compact (82/spl times/60/spl times/30 mm) and versatile single-photon timing module (SPTM), based on a planar epitaxial single photon avalanche diodes (SPAD) working with a monolithic integrated active quenching and active reset circuit (i-AQC) and cooled by a Peltier element. The main operating parameters are computer controlled via RS-232 interface and the photon counting rate can be continuously monitored. The photon detection efficiency is 45% at 500 nm with cooling at -15/spl deg/C, the dark counting rate is 5 c/s with SPAD operating at 5 V excess bias voltage, 10c/s operating at 10 V. The time resolution obtained with tightly focused illumination has 60-ps full-width at half-maximum. Comparative tests with the SPTM prototype and with an advanced commercially available photon counting module confirmed that the time resolution and sensitivity of the SPTM make it possible to resolve and measure even short lifetime components of a single molecule. The SPTM thus made possible experiments leading to a deeper insight into angstrom-scale structural changes of single-protein molecules.     

Implementing a Multiplexed System of Detectors for Higher Photon Counting Rates

Photon counting applications are typically limited by detector deadtime to operate at count rates of a few megahertz, at best, and often at significantly lower levels. This limitation is becoming more critical with the advance of photon counting applications such as photon-based quantum information. We present a first experimental proof of principle, and review the theoretical foundation of a multiplexed detection scheme that allows photons to be counted at higher rates than is possible with individual detectors or simple detector trees. In addition to this deadtime improvement, we discuss the impact of this scheme on other relevant characteristics such as afterpulsing and dark count rates.     

Analysis of Hot-Carrier Luminescence for Infrared Single-Photon Upconversion and Readout

We propose and analyze a new method for single-photon wavelength up-conversion using optical coupling between a primary infrared (IR) single-photon avalanche diode (SPAD) and a complementary metal oxide semiconductor (CMOS) silicon SPAD, which are fused through a silicon dioxide passivation layer. A primary IR photon induces an avalanche in the IR SPAD. The photons produced by hot-carrier recombination are subsequently sensed by the silicon SPAD, thus, allowing for on-die data processing. Because the devices are fused through their passivation layers, lattice mismatch issues between the semiconductor materials are avoided. We develop a model for calculating the conversion efficiency of the device, and use realistic device parameters to estimate up to 97% upconversion efficiency and 33% system efficiency, limited by the IR detector alone. The new scheme offers a low-cost means to manufacture dense IR-SPAD arrays, while significantly reducing their afterpulsing. We show that this high-speed compact method for upconverting IR photons is feasible and efficient.     

A Single Photon Avalanche Diode Implemented in 130-nm CMOS Technology

We report on the first implementation of a single photon avalanche diode (SPAD) in 130 nm complementary metal-oxide-semiconductor (CMOS) technology. The SPAD is fabricated as p+/n-well junction with octagonal shape. A guard ring of p-well around the p+ anode is used to prevent premature discharge. To investigate the dynamics of the new device, both active and passive quenching methods have been used. Single photon detection is achieved by sensing the avalanche using a fast comparator. The SPAD exhibits a maximum photon detection probability of 41% and a typical dark count rate of 100 kHz at room temperature. Thanks to its timing resolution of 144 ps full-width at half-maximum (FWHM), the SPAD has several uses in disparate disciplines, including medical imaging, 3D vision, biophotonics, low-light illumination imaging, etc.     

Toward a 3-D camera based on single photon avalanche diodes

A three-dimensional (3-D) imager is presented, capable of computing the depth map as well as the intensity scale of a given scene. The heart of the system is a two-dimensional array of single photon avalanche diodes fabricated in standard CMOS technology. The diodes exhibit low-noise equivalent-power high-dynamic range, and superior linearity. The 3-D imager achieves submillimetric precision at a depth-of-field of a few meters. This precision was achieved by averaging over 10 000 measurements. The imager operates using a standard laser source pulsed at 50 MHz with 40-mW peak power and requires no mechanical scanning mechanisms or expensive optical equipment.     

Classification of the Operating Modes of Hot-Cathode Parallel-Plane Plasma Diodes

Many specialized theoretical and experimental studies have been carried out on noble-gas plasma diodes in order to determine the operating characteristics of a particular mode. Even though the modes of cesium plasma diodes have been characterized rather completely by Bullis, no comparable summary has been developed for noble-gas systems. In this paper, the operation of hotcathode parallel-plane plasma diodes is reviewed and the characteristics of the anode-glow, ball-of-fire, Langmuir, temperature-limited, low-voltage arc, and tufted-anode modes are classified and discussed in terms of the volt-ampere characteristics for different load lines. The operation of noble-gas diodes is compared to that of cesium diodes and the interpretation of the volt-ampere characteristic is related to available experimental data. The visual characteristics of each mode are also displayed to aid in the interpretation of the behavior. The correlation between theory and a variety of experiments substantiates the contention that the limitation imposed on the diode current by the cathode is responsible for the previous confusion about the various modes of operation.     

Stadium and quasi-stadium laser diodes

We present theoretical and experimental studies on two-dimensional microcavity laser diodes with stadium and quasi-stadium shapes. We report a demonstration of lasing for the first time in a fully chaotic microcavity-a stadium-shaped cavity which is rigorously known to be fully chaotic. We also present systematic studies on quasi-stadium laser diodes for three types of resonator conditions: stable, marginally stable, and unstable. Morphological dependence of lasing characteristics of quasi-stadium laser diodes is elucidated. We also show examples of the application of quasi-stadium laser diodes to beam switching operation and optical signal distribution by using patterned electrodes and the phase locking phenomenon between two resonator modes.     

Spectroscopy With Nanostructured Superconducting Single Photon Detectors

Superconducting single-photon detectors (SSPDs) are nanostructured devices made from ultrathin superconducting films. They are typically operated at liquid helium temperature and exhibit high detection efficiency, in combination with very low dark counts, fast response time, and extremely low timing jitter, within a broad wavelength range from ultraviolet to mid-infrared (up to 6 mum). SSPDs are very attractive for applications such as fiber-based telecommunication, where single-photon sensitivity and high photon-counting rates are required. We review the current state-of-the-art in the SSPD research and development, and compare the SSPD performance to the best semiconducting avalanche photodiodes and other superconducting photon detectors. Furthermore, we demonstrate that SSPDs can also be successfully implemented in photon-energy-resolving experiments. Our approach is based on the fact that the size of the hotspot, a nonsuperconducting region generated upon photon absorption, is linearly dependent on the photon energy. We introduce a statistical method, where, by measuring the SSPD system detection efficiency at different bias currents, we are able to resolve the wavelength of the incident photons with a resolution of 50 nm.     

Passively Mode-Locked 4.6 and 10.5 GHz Quantum Dot Laser Diodes Around 1.55 μm With Large Operating Regime

Passive mode-locking in two-section InAs/InP quantum dot laser diodes operating at wavelengths around 1.55 $mu$m is reported. For a 4.6-GHz laser, a large operating regime of stable mode-locking, with RF-peak heights of over 40 dB, is found for injection currents of 750 mA up to 1.0 A and for values of the absorber bias voltage of 0 V down to −3 V. Optical output spectra are broad, with a bandwidth of 6–7 nm. However, power exchange between different spectral components of the laser output leads to a relatively large phase jitter, resulting in a total timing jitter of around 35 ps. In a 4-mm-long, 10.5-GHz laser, it is shown that the operating regime of stable mode-locking is limited by the appearance of quantum dot excited state lasing, since higher injection current densities are necessary for these shorter lasers. The output pulses are stretched in time and heavily up-chirped with a value of 16–20 ps/nm. This mode of operation can be compared to Fourier domain mode-locking. The lasers have been realized using a fabrication technology that is compatible with further photonic integration. This makes such lasers promising candidates for, e.g., a coherent multiwavelength source in a complex photonic chip.      

Single Photon Counting Module Based on Large Area APD and Novel Logic Circuit for Quench and Reset Pulse Generation

We present the design, implementation, and characterization of a single-photon counting module (SPCM) based on large-area avalanche photodiode (APD) and new logic circuit based on TTL integrated circuits (ICs) for generating precise quench and reset delays. Low dark count rate, high linearity of 2 MHz, maximum dynamic range of 12 MHz, and minimum dead time of 35 ns have been achieved with 0.2 mm peltier-cooled single photon avalanche diode (SPAD) [model C30902S-DTC, Perkin Elmer Optoelectronics (PKI)]. The developed module was fiberized and tested for the detection of fluorescently labeled DNA sequences. Detection sensitivity at the level of single fluorescent molecule has been demonstrated.     

Room-temperature lasing operation of GaInNAs-GaAssingle-quantum-well laser diodes

We have succeeded in demonstrating continuous-wave (CW) operation of GaInNAs-GaAs single-quantum-well (SQW) laser diodes at room temperature (RT). The threshold current density was about 1.4 kA/cm², and the operating wavelength was approximately 1.18 μm for a broad-stripe geometry. Evenly spaced multiple longitudinal modes were clearly observed in the lasing spectrum. The full-angle-half-power far-field beam divergence measured parallel and perpendicular to the junction plane was 4.5° and 45°, respectively. A high characteristic temperature (T₀) of 126 K under CW operation and a small wavelength shift per ambient temperature change of 0.48 nm/°C under pulsed operation were obtained. These experimental results indicate the applicability of GaInNAs to long-wavelength laser diodes with excellent high-temperature performance     

开关-耦合电感DC-DC变换器

本文提出了开关-耦合电感DC-DC变换电路。在针对已经含有开关电感模块和耦合电感模块的DC-DC拓扑族的研究之上,将开关电感和耦合电感进行耦合,使其作为开关-耦合电感发挥作用,进而得到高电压增益、效率得到改善的新式软开关DC-DC变换器。该类变换器集成了含有开关电感模块和耦合电感模块的DC-DC变换器的升压功能,并且同时实现了有源器件的软开关,改善了效率。主要有源器件S在导通的时候实现了零电流导通（ZCS）,减少了它的损耗。关断时漏感能量通过嵌位二极管传递到输出侧,减少了能量损耗、改善了EMI环境。整流二极管能够在零电流（ZCS）情况下关断,此状态优化可以二极管的反向恢复特性,降低反向关断时的损耗。以开关-耦合电感Boost变换器为例进行了该类电路的研究,分别分析了电路的工作原理和周期工作模式,并推导了电压增益的数学公式。在理论指导下,采用200W开关-耦合电感Boost实验样机,证实所提电路理推理的可实施性和准确性。     

带箝位辅助谐振支路的改进型变换器研究

移相控制零电压全桥变换器利用变压器漏感和开关管的寄身电容可实现开关管的零电压开关,为了抑制整流输出寄生振荡,可以在初级加入一个谐振电感和两个箝位二极管构成辅助谐振支路,本文将辅助谐振支路与变压器交换位置,使辅助支路与超前臂相连,不仅抑制了次级寄生振荡和电压过冲,使整流管和箝位二极管工作在软开关条件下,而且减小了箝位二极管上电流有效值,减小了次级占空比丢失和初级通态损耗。分析了改进后变换器的工作原理,并对改进前后的变换器进行了比较。实验结果验证了电路的正确性。     

Effect of nitrogen on the band structure and material gain of In/sub y/Ga/sub 1-y/As/sub 1-x/N/sub x/-GaAs quantum wells

The conduction subband structure of InGaAsN-GaAs quantum wells (QWs) is calculated using the band anticrossing model, and its influence on the design of long-wavelength InGaAsN-GaAs QW lasers is analyzed. A good agreement with experimental values is found for the QW zone center transition energies. In particular, a different dependence of the effective bandgap with temperature when compared to the equivalent N-free structure is predicted by the model and experimentally observed. A detailed analysis of the conduction subband structure shows that nitrogen strongly decreases the electron energies and increases the effective masses. A very small N incorporation is also found to increase the nonparabolicity, but this effect saturates for higher nitrogen contents. Both the In content and well width decrease the effective masses and nonparabolicity of the conduction subbands. Material gain as a function of the injection level is calculated for InGaAsN-GaAs QWs for moderate carrier densities. The peak gain at a fixed carrier density is found to be reduced, compared to InGaAs, for a small N content, but this reduction tends to saturate when the N content is further increased. For the gain peak energy, a monotonous strong shift to lower energies is obtained for increasing N content, supporting the feasibility of 1.55-/spl mu/m emission from InGaAsN-GaAs QW laser diodes.