Optics and Laser Technology | 2021
Optimizing output spectral linewidth of fiber laser utilizing phase-shifted long-period fiber grating
Abstract
Abstract Suppressing nonlinear effects in fiber laser by special fiber gratings has attracted growing attentions. Currently, most researches mainly focus on suppressing stimulated Raman scattering. However, the mitigation of the nonlinear effects, such as self-phase modulation or four wave mixing, which broaden the main lobe of the output laser spectrum has not been paid attention. We report a novel method for universally and conveniently optimizing output spectral linewidth of fiber laser by applying phase-shifted long-period fiber grating (PS-LPFG). A detailed design philosophy and method of PS-LPFG was proposed. Further, a symmetrical PS-LPFG was fabricated to verify the feasibility of the method. The central wavelength of the grating’s passband was designed to match the signal light of a 1075\xa0nm fiber laser. A 200\xa0W continuous-wave oscillator was also established to evaluate the PS-LPFG’s performance. Experimental results demonstrate that the spectral broadening of the main lobe is clearly alleviated. The 30\xa0dB linewidth of the evaluation system is narrowed approximately 32.9% by the PS-LPFG. The 0.03\xa0dB insertion loss of the fabricated grating avoids the deterioration of the signal laser’s power. Furthermore, the 0.023\xa0°C/W thermal slope of the grating allows for potential applications in higher power fiber lasers.