Laser polarization characteristics from phase-shifted grating inscribed by polarized ultraviolet Argon laser

摘要

Phase-shifted grating based distributed feedback fiber lasers with different polarization characteristics were made with Ppolarizedand S-polarized 244nm Argon ion laser separately. In this paper, the laser polarization characteristics from thephase-shifted gratings were investigated experimentally. The narrow linewidth laser emitted from phase-shifted gratingin Erbium doped fiber showed different polarization and wavelength characteristics for incident laser in differentpolarization states and in different doses. By high resolution spectrum analysis, the laser always had two closewavelengths with a gap of several pm which were in two orthogonal polarization states and had similar powers, if thephase-shifted grating was made with a P-polarized (which is paralleled to the the axial fiber) incident laser. The lasershowed evidently different characteristics when the incident laser is in S-polarization (which is perpendicular to the axialfiber). Here, the laser operated in single wavelength mode when irradiated dose was in a range. However, the laseroperated in dual-wavelength mode and dual polarization states when irradiated dose exceeded a threshold. Thewavelength gap increased from several pm to more than 10 pm with the increasing irradiated dose. The power ratio ofthe two wavelengths changed simultaneously.