Spectrum Extreme Purification and Modulation of DBR Fiber Laser With Weak Distributed Feedback

Highly coherent lasers with spectral hyperpurity can further advance the fields of science and engineering. Especially, a light source with controllable frequency domain parameters can be adapted to a variety of emerging application scenarios. Herein, we report on an implementation of a novel ultra-high spectral purity distributed Bragg reflector (DBR) all-fiber laser based on weak distributed feedback, and its spectrum can be modulated in a certain extent by precisely controlling the intensity of the distributed feedback signal. Eventually, an ultra-high spectral purity laser with a spectral signal-to-noise ratio of 64 dB, a side mode suppression ratio (SMSR) of 83 dB, an output Lorentz linewidth of 115 Hz and a relative intensity noise of less than -122 dB/Hz is successfully obtained under normal conditions. Also, the frequency noise limit of the fiber laser with weak distributed feedback in the high frequency white noise flat region is 4.8 Hz(2)/Hz, corresponding to a fundamental linewidth of similar to 15.1 Hz. In particular, the SMSR and Lorentz linewidth of the laser can be continuously adjusted from 53 dB to 83 dB and 115 Hz to 8.2 kHz, respectively. In addition, we also investigated the effect of different pumping configurations on the performance of the DBR fiber laser. The proposed controllable mechanism of laser spectrum also provides a new perspective for extreme regulation of other laser parameters.