Wideband Spectrum Estimation for Photon Counting Heterodyne

Photon counting heterodyne can provide extremely high sensitivity while allowing to reduce the local oscillator power as low as 1 pW, which will promote the advantage in flash coherent imaging. To explore the receiver bandwidth under different count rates in photon counting heterodyne applications, an AMCW-based single photon mechanism is proposed and experimentally demonstrated in this letter. With amplitude-modulated continuous wave (AMCW) technique, an AMCW optical signal with single frequency and low DC component is generated for receiver bandwidth exploration. Afterwards, the spectrum is recovered from the photon arrival sequence under different count rates. Experimental results show that a receiver bandwidth of up to 1 GHz can be estimated from the photon arrival sequence when the count rates ranges from 2 Mcps to 8 Mcps.