Study on laser performance of tapered ytterbium doped fiber in nanosecond pulse amplifier

In this paper, the ytterbium-doped tapered fiber with core/inner cladding diameter varying from 31/250 μm to 62/500 μm was designed and prepared by the improved chemical vapor deposition and solution doping technology. An all-fiber nanosecond pulse amplifier was built based on the ytterbium-doped tapered fiber, and the influence of the longitudinal structure on the output characteristics of nanosecond pulsed laser was investigated. A nanosecond pulsed laser output with a central wavelength of 1064 nm, an average power of 832 W, a single pulse energy of 8.32 mJ and a peak power of 24.8 kW at a repetition rape of 100 kHz was achieved based on the ytterbium-doped tapered fiber with a large diameter uniform region length ratio of 62.5%. Compared with 50/400 μm uniform fiber, the ytterbium-doped tapered fiber showed obvious suppression effect on stimulated Raman scattering and beam degradation at a similar output power.