High-Speed Single-Photon Frequency Upconversion With Synchronous Pump Pulses

Single-photon signals at 1.56 ¿m were converted into the visible region by sum-frequency generation, with synchronous pump pulses at 1.03 ¿m in a periodically poled lithium niobate crystal. The signal and pump sources were provided by two synchronized mode-locked fiber lasers at the operation rate of 7.88 MHz. Such a high-speed single-photon upconversion system has shown an overall detection efficiency of 10.4%. The corresponding background noise was measured to be 3.3 × 10
³
s
^-1
. The noise-equivalent power in this scheme was 9.93 × 10
^-17
W/Hz
^1/2
, which was the lowest compared to the other upconversion systems with similar pump and signal wavelengths.