High-order actively mode-locked picosecond fiber laser and Poissonian single-photon source

Abstract

We propose a novel scheme of high-order actively mode-locked picosecond fiber laser based on the nonlinear polarization rotation in a semiconductor optical amplifier, and experimentally demonstrate the 200th-order mode locking with repetition frequency of ∼ 1.19 GHz and pulse width of 1.63 ps. The fundamental repetition frequency is accurately obtained to be 5.9639 MHz by spectrum analysis. Our laser is much easier mode locked and stabler than passive mode-locked ones. Taking advantage of the ultra-stable mode-locked laser, we obtain practical quasi-single-photon (QSP) source. Statistic analyses show that it approaches closer to the Poisson distribution at lower count rate. In our experiment, at count rate of 9.7 kcps or QSP emitting rate of ∼97 kcps, it obeys a perfect standard Poisson distribution. The laser is convenient to be upgraded for higher-order mode-locked at repetition frequency over 40 GHz, which are suitable to generate high-speed QSP source for future quantum communications.