Polarization-maintaining amplifier based on 3C fiber structures

Chirally-Coupled-Core (3C) fiber structure can preserve a single mode quality and even a linear polarization for a large core size. A principal advantage of fiber laser is its compatibility with monolithic integration and robust system. But so far, devices such as a combiner using the 3C fibers have not been reported. Here we report the first demonstration of such monolithic amplifier structure which contains an active fiber and a combiner based on 3C fibers. A single-stage amplifier is seeded by an EO Q-switched micro-laser and pumped by two high power fiber pigtailed 976-nm laser diodes via an in-house fabricated (2 + 1) × 1 pump signal combiner. The active fiber is based on a 3-m-long, 3C Yb-doped fiber (33 μm/250 μm core/cladding diameter with 0.06/0.46 NA). The amplifier demonstrates scaling up to 30W average power and 150 kW peak power in 0.3mJ, 2ns pulses. The beam profiles and beam qualities were characterized as its output power was varied up to 30W. The beam profile was maintained at a high beam quality of around M 2 =1.2. The spectral properties of the 3C fiber were also characterized as its output peak power was varied.