Quinlan Franklyn, Baynes Fred N, Fortier Tara M, Zhou Qiugui, Cross Allen, Campbell Joe C, Diddams Scott A
Opt Lett. 2014 Mar 15;39(6):1581-4. doi: 10.1364/OL.39.001581.
We investigate the impact of pulse interleaving and optical amplification on the spectral purity of microwave signals generated by photodetecting the pulsed output of an Er:fiber-based optical frequency comb. It is shown that the microwave phase noise floor can be extremely sensitive to delay length errors in the interleaver, and the contribution of the quantum noise from optical amplification to the phase noise can be reduced ∼10 dB for short pulse detection. We exploit optical amplification, in conjunction with high power handling modified unitraveling carrier photodetectors, to generate a phase noise floor on a 10 GHz carrier of -175 dBc/Hz, the lowest ever demonstrated in the photodetection of a mode-locked fiber laser. At all offset frequencies, the photodetected 10 GHz phase noise performance is comparable to or better than the lowest phase noise results yet demonstrated with stabilized Ti:sapphire frequency combs.
我们研究了脉冲交织和光放大对通过光电探测基于铒光纤的光频梳的脉冲输出所产生的微波信号频谱纯度的影响。结果表明，微波相位噪声基底对交织器中的延迟长度误差可能极其敏感，并且对于短脉冲探测，光放大产生的量子噪声对相位噪声的贡献可降低约10 dB。我们利用光放大，并结合高功率处理的改进型单载流子光电探测器，在10 GHz载波上产生了-175 dBc/Hz的相位噪声基底，这是锁模光纤激光器光电探测中迄今所展示的最低值。在所有偏移频率下，光电探测到的10 GHz相位噪声性能与稳定的钛宝石频率梳迄今所展示的最低相位噪声结果相当或更好。
