Research On Integrated Circuits For Near Infrared Single Photon Detection

Single photon detection is an extremely low-light-level detection technology, that many countries are pursuing. It has great prospects in a lot of fields, such as, quantum information, bio-imaging, space laser communications, LADAR, as-tronomy, and other areas of low visual target detection. Especially due to the near-infrared band has two low-loss window in optical fiber communication, is eye-safe and is also suitable for the night vision, near-infrared single photon detec-tion attracts more attention. In visible band, the silicon avalanche photodiode serves as ideal single-photon detector element; and in the near infrared band, InGaAs/InP avalanche photodiode has a great advantage. Unlike conventional linear mode, the avalanche photodiode is biased above its breakdown voltage, that is called Geiger mode, where the avalanche photodiode has infinite gain. When a photon enters the active area, it can trigger a self-sustainable avalanche, generating a detectable electric signal. Although Geiger mode avalanche photo-diodes can detect a single photon, it also brings a series of problems such as dark counts, afterpulses and other issues. And for single photon imaging, it is neces-sary to process the signal of avalanche photodiode array. Therefore, the design of integrated circuits for InGaAs/InP single photon avalanche diodes becomes a key issue.The main content of this thesis is to study integrated circuits matching the lab-made InGaAs/InP single photon avalanche diodes. The main innovations include the following aspects:(1) Two high-speed single-photon detection circuitsTraditional gating circuits using external logic gates can only reach about 20 MHz frequency gating and it is difficult to achieve very narrow gate. To solve these problems, combining a low-cost flexible configurable FPGA and high-speed ECL comparators, we design a miniaturized adjustable 100MHz near-infrared single photon detector based FPGA. Meanwhile, it plays a significant role in testing the performance of a single photon avalanche diode.To extract the weak avalanche signal, taking advantage of differential circuit, this thesis presents double balanced differential high-speed circuit configuration. Two adjacent single photon avalanche diodes (SPADs) from the same wafer are configured as the first balanced structure, and the output signal from the first balanced stage is subtracted by the phase-shifted attenuated gate driving signal as the second balanced stage, that can effectively discriminate weak avalanche signal, and achieve 400 MHz gating frequency.These two high-speed single photon detector are simple and reliable, and provides a guideline for the integrated high-speed design.(2) Two quenching circuits matching lab-made InGaAs/InP SPADDue to the small band-gap InGaAs material, dark counts caused by thermal noise are high, so InGaAs/InP SPADs generally operate in gated mode. However, in many applications, such as LADAR, photons arrive in a random fashion, not synchronized with the gating signal, so InGaAs/InP SPADs also need to work in free-running mode. We designed an active feedback quenching active recovery integrated circuit to quench avalanche quickly, and to recover to quiescent state quickly. This can reduce the avalanche current flowing through the device to a large extent, thereby reducing the phenomenon of afterpulsing.Understanding the process of the avalanche process, passive quenching is very fast, but the passive recovery process is very slow. So taking advantage of this feature, this thesis presents a mixed passive variable load quenching active recovery integrated circuit. Although the quenching is slow, overshoot is largely reduced.Both the quenching circuits match well with the electronic characteristic of lab-made InGaAs/InP SPAD, and are able to achieve a series of actions of sensing, quenching, dead-time control, recovery, and counting.(3) Multi-photon detection circuit and array integrated circuitGeiger mode avalanche photodiode can only detect presence or absence of photons, can not resolve photon number. This thesis proposes a multi-photon detector, based on single pixel circuits with active quenching, achieving a reso-lution of 15 photons. Output pulses from different pixels are superimposed into one pulse that is proportional to the number of photons. The voltage pulse can be matched directly with the laser rangefinder products.Array readout is the key issue for achieving single-photon imaging, the thesis conducted a detailed analysis and design on key array readout:array integration and bus readout. The thesis implemented 1×8 line array and 8x8 planar array of high consistence within pixels. As to 8x8 array, full parallel integrated scheme is adopted; pixel data is sequentially read out, and is sent out through UART bus, laying solid foundation for larger array integration.