Maintaining the Polarization, Temperature and Amplification Characteristics of a Ytterbium-doped Rod-type Photonic Crystal Fiber (PCF) Amplifier

We report on the single frequency ytterbium (Yb)-doped end-capped 81-cm rod-type photonic crystal fiber (PCF) amplifier. At a pump power of 250 W and 4 W seed power input, the CW PCF amplifier was found to generate average output powers of 138 W, 110 W, and 82 W in 1056 nm, 1070 nm, and 1089 nm wavelengths, respectively. The amplified PCF output beam has a line width of 70 MHz in full width half maximum (FWHM). These PCF amplified beams have good beam qualities with M^2 values of less than 1.8 in all three wavelengths. The gain saturation seed input power in 81-cm PCF found to be ∼6 W at 1056 nm. Temperature of the PCF core reached over 230℃ at the pumping section of the PCF. The temperatures of the end-cap head in both pumping and output end-cap sides were 81.4℃ and 35.7℃, respectively. The PCF amplifier shows good polarization maintaining mode characteristics with an average degree of polarization over 87%. Slight decreasing of degree of polarization (DOP) over 170 W output power may caused by variation of the air hole diameter and asymmetry of the PCF structure. KCI Citation Count: 2