Design Of Single-photon Differential Detection Circuit Based On GHz Gating

Single photon detection technology based on Avalanche Photodiode(APD),because of its ultra-high sensitivity photoelectric detection performance,has been widely used in many fields such as quantum communication and laser ranging.At present,the APD detection circuit based on the wide-gated working mode can detect randomly arriving photons.However,this working mode has the disadvantages of large dark count and complicated quenching structure.The single-photon detection technology based on GHz gated fixed quenching can not only effectively solve the above problems,but also detect the photons that reach the gated exposure window according to the predicted timing.It has laid an important foundation in quantum communication applications.Due to the parasitic junction capacitance of the APD,when the gated signal is coupled to the cathode of the APD,its transition edges will generate large spike noise signals through the APD.The spike noise will produce different degrees of aliasing with the avalanche signal.It significantly increases the difficulty of effectively extracting avalanche signals from spike noise.In this paper,the detector and spike noise were first modeled and analyzed.The characteristics of the avalanche signal and the key factors affecting the gated spike noise were determined.In addition,the detection method of differential common mode suppression is also determined.That is,the dual APD main and auxiliary induction branches are constructed.Only the main branch APD can receive light normally.The LNA is used to suppress the two peak noises as a common-mode signal.If there is a triggered avalanche signal,it can be amplified as a differential signal to trigger the subsequent comparator output state inversion to achieve single photon detection.The LNA adopts a g_m-boosted CG structure to achieve the requirement of input impedance matching and voltage gain,under the low power consumption.The comparator uses the structure of pre-amplification combined with dynamic latch to meet the needs of high-speed detection of the detection circuit.Based on TSMC 0.18?m CMOS process,the single-photon differential detection circuit is completed on Cadence platform.The test results show that the model of the detector and the gated spike noise is correct.Under ideal incentive condition,the detection circuit functions correctly,but the performance is degraded compared with the simulation result.The voltage gain of the LNA is 17.9d B.The transmission delay of the comparator is 3.2ns and the resolution is 173.8m V.The system transmission delay is 5ns.Under the condition of loading APD,the circuit noise tolerance is 155m V.Due to the limited test conditions of GHz narrow-gated,the method of using external signal injection or APD dark count equivalent to replace the avalanche signal is used for testing.Under the condition of differential detection with the spike noise matching,the circuit has the detection capability of GHz gating.Finally,the reasons for the degradation of test results are analyzed in detail,and some feasible improvement schemes are given.