1.3- mu m Nd:YAG crystal fiber amplifiers

Using unclad Nd:YAG crystal fibers of 10-40 mu m diameter and 1 cm long, and a laser diode pumping power of 83 mW at a wavelength of 0.81 mu m, gains of up to 6.5 dB at 1.32 mu m have been observed. No significant dependence of gain on signal polarization or output signal level between -43 and -5.4 dBm was observed for a 16 mu m diameter fiber. For smaller diameter fibers and a reduction of the competition from amplified spontaneous emission (ASE) at 1.064 mu m, much higher gains are expected. Extrapolation of experimental and theoretical results predicts gains in excess of approximately 30 dB for fiber diameters of 5 mu m.<>