Zhao Jian, Guiraud Germain, Floissat Florian, Gouhier Benoit, Rota-Rodrigo Sergio, Traynor Nicholas, Santarelli Giorgio
Opt Express. 2017 Jan 9;25(1):357-366. doi: 10.1364/OE.25.000357.
Gain dynamics study provides an attractive method to understand the intensity noise behavior in fiber amplifiers. Here, the gain dynamics of a medium power (5 W) clad-pumped Yb-fiber amplifier is experimentally evaluated by measuring the frequency domain transfer functions for the input seed and pump lasers from 10 Hz to 1 MHz. We study gain dynamic behavior of the fiber amplifier in the presence of significant residual pump power (compared to the seed power), showing that the seed transfer function is strongly saturated at low Fourier frequencies while the pump power modulation transfer function is nearly unaffected. The characterization of relative intensity noise (RIN) of the fiber amplifier is well explained by the gain dynamics analysis. Finally, a 600 kHz bandwidth feedback loop using an acoustic-optical modulator (AOM) controlling the seed intensity is successfully demonstrated to suppress the broadband laser intensity noise. A maximum noise reduction of about 30 dB is achieved leading to a RIN of -152 dBc/Hz (~1 kHz-10 MHz) at 2.5 W output power.
增益动力学研究为理解光纤放大器中的强度噪声行为提供了一种有吸引力的方法。在此，通过测量从10 Hz至1 MHz的输入种子光和泵浦光的频域传递函数，对一个中等功率（5 W）包层泵浦的镱光纤放大器的增益动力学进行了实验评估。我们研究了在存在显著残余泵浦功率（与种子光功率相比）的情况下光纤放大器的增益动态行为，结果表明种子光传递函数在低傅里叶频率下强烈饱和，而泵浦功率调制传递函数几乎不受影响。增益动力学分析很好地解释了光纤放大器相对强度噪声（RIN）的特性。最后，成功演示了一个使用声光调制器（AOM）控制种子光强度的600 kHz带宽反馈环路，以抑制宽带激光强度噪声。在2.5 W输出功率下实现了约30 dB的最大噪声降低，导致RIN为-152 dBc/Hz（~1 kHz - 10 MHz）。
