Hou Yubin, Zhang Qian, Wang Pu
Opt Express. 2016 Jun 13;24(12):12991-9. doi: 10.1364/OE.24.012991.
The frequency and intensity noise of an Yb-doped single-frequency distributed Bragg reflector (DBR) fiber laser are effectively reduced by a simple, passive optical-feedback loop (POFL), which consists of only two optical couplers. The feedback loop, which has resonance with the high reflective grating of the DBR laser and relative long optical path compared to the DBR cavity, results in narrower linewidth and lower relative intensity noise (RIN) in the feedback signal. The RIN of relaxation oscillation is reduced by 20dB from -99.9dB/Hz @ 993 kHz to -119.4dB/Hz @ 192 kHz, and the frequency noise was suppressed at frequencies higher than 1 kHz, with a maximum reduction of about 30 dB from 10 kHz to 100 kHz, which results in a spectral linewidth compression from 3.96 kHz to 540 Hz. Even after one fiber amplification stage, the noise did not increase significantly, and a spectral linewidth well below 1 kHz were also achieved at output power of 10W.
通过一个简单的无源光反馈环路（POFL），有效降低了掺镱单频分布布拉格反射（DBR）光纤激光器的频率和强度噪声，该环路仅由两个光耦合器组成。该反馈环路与DBR激光器的高反射光栅发生共振，并且与DBR腔相比具有相对较长的光路，从而使反馈信号的线宽变窄，相对强度噪声（RIN）降低。弛豫振荡的RIN从993kHz时的-99.9dB/Hz降低了20dB至192kHz时的-119.4dB/Hz，并且在高于1kHz的频率处频率噪声得到抑制，从10kHz到100kHz最大降低约30dB，这导致光谱线宽从3.96kHz压缩到540Hz。即使经过一级光纤放大，噪声也没有显著增加，并且在10W的输出功率下也实现了远低于1kHz的光谱线宽。
