Research On The Noise Suppression Of 1.5?m Single-frequency Fiber Laser

Single-frequency fiber lasers have the wide application prospects in the fields of laser cooling,high-precision spectroscopy,microwave generation,fiber-optical communication,LIDAR and gravitational wave detection and so on,which is due to their numerous advantages that include compact all-fiber structure,good beam quality,high signal noise ratio,low noise,narrow linewidth and stable single-longitudinal-mode operation and so on.And in optical fiber sensing,LIDAR,gravitational wave detection and other application fields,the linewidth and the intensity noise of the lasers both limit the performance of the system strongly.Therefore,conducting the research on suppressing the noise of the single-frequency fiber lasers is beneficial to expand the application fields of single-frequency fiber lasers and promotes the technological development of these fields.This paper studies the noise suppression technology of the 1.5 ?m single-frequency fiber lasers and the results are as follows:(1)Based on the mechanism that the intensity noise of pump contributes to the noise of fiber laser,the research on simultaneously suppressing the linewidth and intensity noise of the 1.5 ?m single-frequency fiber laser is carried out.The optoelectronic feedback combined with the low-noise pump is used to optimize the intensity noise of pump of the fiber laser.After optimizing the pump noise,the linewidth of the single-frequency fiber laser is compressed from 1.3 kHz to 650 Hz and the relative intensity noise is also reduced by 7~11.5 dB and 3~7 dB in the frequency range of 0.2~5 kHz and 5~10 kHz respectively.At 1 kHz,the intensity noise is reduced to about-145 dB/Hz@0.5 mW.(2)Combining the self-injection locking and optimizing pump noise,the research on suppressing the intensity noise and compressing the linewidth of the 1.5 ?m single-frequency fiber laser is conducted.In the experiment,the single-frequency laser output with the Lorentz linewidth of 88.7 Hz is achieved and the relative intensity noise is reduced to <-146.5 dB/Hz@0.5 mW in the frequency range of 1~10 kHz,the peak value of relaxation oscillation peak is also reduced by 48 dB to-127.7 dB/Hz.(3)Utilizing the saturated semiconductor optical amplifier(SOA)combined with the optoelectronic feedback,the research on suppressing the intensity noise of the 1.5 ?m single-frequency fiber laser with self-injection locking after optimizing pump noise is conducted.In the experiment,the relative intensity noise is suppressed to <-154.5 dB/Hz@1 mW in the frequency range of 1~10 MHz,which is within 1.5 dB from the shot-noise limit.The relative intensity noise also is reduced to <-151.5 dB/Hz@1 mW in the frequency range of 2.5~10 kHz,which is within 4.5 dB from the shot-noise limit.