Performance optimization of InGaAs/InP SPADs for either low noise or high photon detection efficiency applications

InGaAs/InP Single-Photon Avalanche Diodes ( SPADs) can achieve high photon detection efficiency (PDE) with a thick absorber, but at the expense of higher dark count rate ( DCR). PDE and DCR also depend on the electric field inside the structure, which can be tailored in the design phase and influences the overall performance. We present the design and the experimental characterization of two different 10 mu m-diameter InGaAs/InP SPADs. The first one is intended for applications where low noise is the key requirement: at 225 K and 5 V excess bias, it features 1 kcps DCR, 25% PDE at 1550 nm and a timing jitter of 100 ps (FWHM). The second device is an InGaAs/InP SPAD optimized for PDE-enhanced applications, having a PDE up to 50% at 1550 nm, with a DCR of 20 kcps and a timing jitter of 70 ps (FWHM) at 225 K. Alternatively, it features a PDE of 37% at 1550 nm, with a DCR of just 3 kcps and a timing jitter of 100 ps (FWHM). When combined with a custom integrated circuit we developed, both devices show an afterpulsing probability as low as few percent with a gating frequency of 1 MHz and hold-off time of few microseconds at 225 K, allowing to achieve a photon count rate towards 1 Mcps

An extremely low-noise heralded single-photon source: a breakthrough for quantum technologies

Low noise single-photon sources are a critical element for quantum technologies. We present a heralded single-photon source with an extremely low level of residual background photons, by implementing low-jitter detectors and electronics and a fast custom-made pulse generator controlling an optical shutter (a LiNbO3 waveguide optical switch) on the output of the source. This source has a second-order autocorrelation g^{(2)}(0)=0.005(7), and an "Output Noise Factor" (defined as the ratio of the number of noise photons to total photons at the source output channel) of 0.25(1)%. These are the best performance characteristics reported to date

Hong-Ou-Mandel interference between independent III-V on silicon waveguide integrated lasers

The versatility of silicon photonic integrated circuits has led to a widespread usage of this platform for quantum information based applications, including Quantum Key Distribution (QKD). However, the integration of simple high repetition rate photon sources is yet to be achieved. The use of weak-coherent pulses (WCPs) could represent a viable solution. For example, Measurement Device Independent QKD (MDI-QKD) envisions the use of WCPs to distill a secret key immune to detector side channel attacks at large distances. Thus, the integration of III-V lasers on silicon waveguides is an interesting prospect for quantum photonics. Here, we report the experimental observation of Hong-Ou-Mandel interference with 46\pm 2% visibility between WCPs generated by two independent III-V on silicon waveguide integrated lasers. This quantum interference effect is at the heart of many applications, including MDI-QKD. Our work represents a substantial first step towards an implementation of MDI-QKD fully integrated in silicon, and could be beneficial for other applications such as standard QKD and novel quantum communication protocols.Comment: 5 pages, 3 figure

Low-Noise InGaAs/InP Single-Photon Avalanche Diodes for Fiber-Based and Free-Space Applications

We present the design and the experimental characterization of a new InGaAs/InP single-photon avalanche diode (SPAD), with two different diameters: i) a 10 m device, suitable for optical fiber-based quantum applications; ii) a 25 m one, more appropriate for free-space applications. Compared to a previous generation, we improved the design of the double zinc diffusion and optimized the layer structure. We achieved low dark count rate, around 1 kcps and 4 kcps at 225 K and 5 V excess bias for 10 m and 25 m devices, respectively, and down to few tens of counts per seconds at 175 K for the 10 m detector. At 5 V excess bias and 225 K temperature, both devices also show a high photon detection efficiency (33% at 1064 nm, 31% at 1310 nm and 25% at 1550 nm for the 10 m SPAD). Afterpulsing has been measured with a custom readout integrated circuit, achieving very low probability values. Timing jitter is comparable to previous-generation devices

Fully programmable single-photon detection module for InGaAs/InP single-photon avalanche diodes with clean and sub-nanosecondgating transitions

We present the design and characterization of a modern near-infrared photon counting module, able to exploit the best performance of InGaAs/InP single-photon avalanche diodes for the detection of fast and faint optical signals up to 1.7 μm. Such instrument is suitable for many applications, thanks to the user-friendly interface and the fully adjustable settings of all operating parameters. We extensively characterized both the electronics and the detector, and we validated such instrument up to 133 MHz gate repetition frequency, for photon-counting and photon-timing applications, with very clean temporal response and excellent timing performance of less than 100 ps

Photon counting module based on InGaAs/InP Single-Photon Avalanche Diodes for near-infrared counting up to 1.7 µm

InGaAs/InP Single-Photon Avalanche Diodes (SPADs) have good performance to be successfully employed in many applications that demand single photon detection in the 1 - 1.7 μm wavelength range. However, in order to fully exploit such detectors, they have to be operated in optimized working conditions using dedicated electronics. We present the design and experimental characterization of a high-performance compact detection module able to operate at best InGaAs/InP SPADs. The module includes a pulse generator for gating the detector, a front-end circuit for avalanche sensing, a fast circuitry for detector quenching and resetting and some sub-circuits for signal conditioning. Experimental measurements prove the state-of-the-art performance and its great flexibility to fit the different applications

Fast Active Quenching Circuit for Reducing Avalanche Charge and Afterpulsing in InGaAs/InP Single-Photon Avalanche Diode

We characterize three different quenching circuits for InGaAs/InP single-photon avalanche diodes (SPADs) operated in gated mode: i) a simple passive quenching circuit; ii) an active quenching circuit; and iii) a fast active quenching circuit. For each of these, we acquire the shape of the avalanche current, at different excess biases, by reconstructing the waveform of the photons emitted from the detector during an avalanche and we simultaneously measure the afterpulsing probability and the dependence of dark count rate on gate period (to estimate the maximum count rate). We prove that the avalanche charge reduction is in agreement with the reduction of afterpulsing probability, giving a four-time decrease in afterpulsing when employing the fast active quenching circuit compared to the simple passive quenching circuit

InGaAs/InP SPAD detecting single photons at 1550 nm with up to 50% efficiency and low noise

We present an InGaAs/InP single-photon avalanche diode (SPAD) with high photon detection efficiency and low noise for fiber-based quantum optics applications. Compared to previous InGaAs/InP SPADs, the InGaAs absorption layer is thicker, to maximize the quantum efficiency. The double zinc diffusion has been adjusted to avoid premature edge breakdown, with the help of a guard ring structure. Our detector achieves a photon detection efficiency up to 50% at 1550 nm, with a dark count rate of 20 kcps and a timing jitter of ∼ 70 ps (FWHM) at 225 K. Alternatively, it features a photon detection efficiency of 37% at 1550 nm, with a dark count rate of just 3 kcps and a timing jitter of ∼ 100 ps (FWHM). When combined with a custom integrated circuit, afterpulsing probability is as low as few percent with a gating frequency of 1 MHz and hold-off time of few microseconds at 225 K, allowing to achieve a photon count rate of almost 1 Mcps

32 Channels SPAD Array for Single Photon Timing Applications

Many applications require photodetectors with single-photon sensitivity and high timing resolution. We present a module based on a linear array of 32 Single-Photon Avalanche Diodes (SPADs) for multi-channel Time-Correlated Single-Photon Counting (TCSPC) applications. Each pixel includes a 30 μm active area diameter SPAD and quenching and counting electronics. We measured a timing resolution of about 110 ps, a photon detection efficiency of 40% at λ = 420 nm and a very low dark count rate of about 150 cps at room temperature