25W, 2µm Broadband Polarization-Maintaining Hybrid Ho- and Tm-Doped Fiber Amplifier
Current developments in LIDAR and atmospheric sensing experiments highlight the need for multi-watt, large bandwidth, high dynamic range polarization-maintaining optical amplifiers in the eye safe 1.9-2.15 mm band. So far, as an illustration of the previous state of the art for high power devices, multi-watt Tm-doped fiber amplifiers (TDFAs) have been demonstrated by Goodno et al. with an output power of 608 W at a signal wavelength of 2040 nm. As for Ho-doped fiber amplifiers (HDFAs) Hemming et al. have reported output powers of 265 W at 2110 nm. For this HDFA, a double clad Ho-doped fiber pumped by high power fiber lasers made the configuration complex and yielded an optical slope efficiency of 41%. Both of these achievements were with standard (non-polarization-maintaining) fiber.