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.     

InGaAsP–InP Avalanche Photodiodes for Single Photon Detection

In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data.     

基于国产InGaAs/InP APD的高速单光子探测

InGaAs/InP雪崩光电二极管(InGaAs/InP APD)是近红外单光子探测器的核心器件之一,其国产化已成为趋势.InGaAs/InP APD工作于1.25 GHz门控盖革模式下,由于APD本身的电容特性,单光子触发产生的雪崩电信号被尖峰噪声所湮没,采用低通滤波的方法可以将有效雪崩信号从尖峰噪声提取出来.为了探讨国产APD的参数水平,对不同温度不同探测效率下国产InGaAs/InP APD的暗计数及后脉冲概率,时间抖动性等相关性能参数进行了测量,并与国外数据进行了对比.当国产InGaAs/InP APD工作于-25 ℃,探测效率10 ％时,暗计数可低至9.9 X10 7/gatc,后脉冲仅为1.5这表明在InGaAs/InP APD这一领域,我国已接近国外水平,但仍有一定的进步空间.     

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.     

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.     

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.     

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.     

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.     

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.     

Low-power compact tunable quenching configuration for minimizing afterpulsing in single-photon avalanche diodes

This paper unveils two efficient free running (FR) quenching circuits with the aim of reducing quenching time (QT) to minimize avalanche charge. Likewise, one circuit is compactly designed with low power consumption, suitable for single-photon avalanche diode ( SPAD) with hold-off time below 10 ns. In second circuit, tunable hold-off and reset-time are provided within a wide range without decreasing QT, which are desirable in many applications. Proper operation and circuit uncertainty is assessed by Monte Carlo analysis in a standard 90-nm complementary metal-oxide semiconductor (CMOS) technology. In a bid to do a comparison between previously reported circuits and the proposed circuits, they are simulated with same SPAD model and parameters and results corroborate the proposed circuits guarantee active quenching time (AQT) of below 1 ns. Proposed circuits with current and area consumption of 0.74 μA, 32 μm² for 7-ns dead time and 16.2 μA, 93 μm² for 21-ns dead time are more efficient in terms of QT, area, and power consumption in comparison with other works.     

High-speed and low-noise avalanche photodiode operating at 1.06μm

Previously, it has been demonstrated that resonant-cavity-enhanced, quantum-dot avalanche photodiodes can achieve a good gain and high quantum efficiency at 1.06 μm. In our new effort, these devices have shown RC-limited bandwidths of 35 GHz at low gain and gain-bandwidth products as high as 220 GHz. The achievable gain has been increased from ~18 to greater than 50 while keeping the quantum efficiency high. These photodiodes also exhibited low avalanche noise (k=0.24), low dark current (less than 100 nA at 90% of the breakdown voltage), and low-breakdown voltage (~17 V)     

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.     

Operational Analysis of a Quantum Dot Optically Gated Field-Effect Transistor as a Single-Photon Detector

We report on the operation of a novel single-photon detector, where a layer of self-assembled quantum dots (QDs) is used as an optically addressable floating gate in a GaAs/Al_0.2Ga_0.8As delta-doped field-effect transistor. Photogenerated holes charge the QDs, and subsequently, change the amount of current flowing through the channel by screening the internal gate field. The photoconductive gain associated with this process makes the structure extremely sensitive to light of the appropriate wavelength. We investigate the charge storage and resulting persistent photoconductivity by performing time-resolved measurements of the channel current and of the photoluminescence emitted from the QDs under laser illumination. In addition, we characterize the response of the detector, and investigate sources of photogenerated signals by using the Poisson statistics of laser light. The device exhibits time-gated, single-shot, single-photon sensitivity at a temperature of 4 K. It also exhibits a linear response, and detects photons absorbed in its dedicated absorption layer with an internal quantum efficiency (IQE) of up to (68 plusmn18)%. Given the noise of the detection system, the device is shown to operate with an IQE of (53 plusmn 11)% and dark counts of 0.003 counts per shot for a particular discriminator level.     

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.     

Photonic Applications With the Organic Nonlinear Optical Crystal DAST

We review the recent progress in the development of photonic applications based on the organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). DAST is an organic salt with an extremely high nonlinear optical susceptibility chi⁽²⁾(-2omega,omega,omega)=580plusmn30 pm/V at 1.54 mum, a high electrooptic figure of merit n ³ r = 455plusmn80 pm/V at 1.54 mum, as well as a low dielectric constant epsiv = 5.2 . DAST is, therefore, very attractive for high-speed optical modulators and field detectors, as well as for frequency conversion and the generation of terahertz waves. Several techniques to microscopically structure this material have been developed recently; including modified photolithography, photobleaching, femtosecond laser ablation, graphoepitaxial growth, ion implantation, and direct electron-beam structuring, which open new perspectives of using this exceptional material for high-speed very-large-scale integrated photonics.     

Injection and Avalanche Electroluminescence of $hbox{Al}_{hbox{0.1}} hbox{Ga}_{hbox{0.9}} hbox{N/Al}_{hbox{0.15}} hbox{Ga}_{hbox{0.85}} hbox{N}$ Multiple Quantum Wells

Three periods of Al_0.1Ga_0.9N/Al_0.15Ga_0.85 N multiple quantum wells (MQWs) were used as the active region of a p-i-n diode fabricated on 6H-SiC substrate. Electroluminescence (EL) of these MQWs has been investigated in both injection and avalanche modes. Band-to-band luminescence of the Al_0.1Ga_0.9N wells was found to peak at 364 nm in the injection mode and in the range of 364-372 nm in the avalanche mode. The most striking phenomenon is that band-to-band EL of the Al_0.15Ga_0.85N barriers has also been observed in the injection mode, while it is not seen in the avalanche mode. This is explained by considering different sources of carriers and different carrier transportation mechanisms in the two modes. The luminescence intensity I _EL has a power-law dependence on the current I by I _EL prop I ² in the injection mode and by I _EL prop I ⁴ in the avalanche mode.     

Superconducting Nanowire Single-Photon Detectors for Quantum Information and Communications

Superconducting nanowire single-photon detectors (SNSPDs or SSPD) are highly promising devices in the growing field of quantum information and communications technology. We have developed a practical SSPD system with our superconducting thin films and devices fabrication, optical coupling packaging, and cryogenic technology. The SSPD system consists of six-channel SSPD devices and a compact Gifford–McMahon (GM) cryocooler, and can operate continuously on 100 V ac power without the need for any cryogens. The SSPD devices were fabricated from high-quality niobium nitride (NbN) ultrathin films that were epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices were temperature stabilized to 2.96 K $pm$ 10 mK. The system detection efficiency for an SSPD device with an area of 20 $times$ 20 $mu$m$^2$ was found to be 2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count rate of 100 Hz, and a jitter of 100 ps full-width at half maximum. We also performed ultrafast BB84 quantum key distribution (QKD) field testing and entanglement-based QKD experiments using these SSPD devices.      

GaAsSb: a novel material for near infrared photodetectors on GaAs substrates

We have studied the molecular beam epitaxy (MBE) growth of GaAsSb on GaAs substrates. The optical properties and composition of GaAsSb layer strongly depend on the growth temperature, the Ga growth rate, and the As and Sb fluxes and their ratios. We also report on two GaAsSb-GaAs photodiode structures operating at 1.3 /spl mu/m. The peak quantum efficiency was 54% for the GaAsSb resonant-cavity-enhanced (RCE) p-i-n photodiode and 36% for the RCE GaAsSb avalanche photodiode (APD) with separate absorption, charge, and multiplication regions (SACM). At 90% of the breakdown, the dark current of the SACM APD was 5 nA. The GaAsSb SACM APD also exhibited very low multiplication noise and k/sub eff/ was approximately 0.1, which is the lowest ever reported for APDs operating at 1.3 /spl mu/m.     

Fast and slow electrons in liquid Ar and N2 mixtures

Fast and slow electron current signals in N₂/Ar liquid mixtures have been observed. From the fast signal, the drift velocity and life time of delocalized electrons in the liquid with N₂ molar fractions X=N₂/(N₂+Ar) below 20 mol% were obtained for field strengths E between 5 and 45 kV/cm. The mobility for delocalized electrons in the liquids was shown to decrease exponentially with X as indicated in a previous paper. However, the mobility for localized electrons was shown to increase with increasing X, but only slightly around the N₂ liquid value