Photon Counting Heterodyne With a Single Photon Avalanche Diode

To implement high sensitivity, good anti-interference and low data rate simultaneously in optical heterodyne system, a photon counting heterodyne mechanism is proposed in this letter. Due to the stochastic behavior, a single photon avalanche diode (SPAD) is used as both a photon collector and a sparse sampler. On the one hand, it allows to reduce the power of the intermediate frequency (IF) signal to 1 picowatt or lower. On the other hand, it enables to generate fewer data samples while recovering the spectrum based on compressive sampling (CS). Compared with direct FFT method that recovers the spectrum by FFT directly, the CS method uses the photon arrival sequence as a measurement to recover the spectrum of the IF signal and suppress other frequency components. Therefore, a higher signal-to-noise ratio (SNR) can be implemented. Experimental results show that the SNR of the CS method is approximately 15 dB higher than that of the direct FFT method. In addition, the photon counting heterodyne achieve better anti-interference capability than classical heterodyne.