Realization of uniform transverse gain in an edge-pumped multislab pulsed amplifier with a gradient profile doping

Abstract

Gradient doping ensures uniform transverse gain in an edge-pumped multislab pulsed amplifier, and a 1D iterative method is developed to generate the proper doping profile. Our investigations show that uniform gain under short pump duration tp = 0.25 ms can be readily achieved, where the modulation of the gain distribution is lower than 1.05 even if the diagonal transverse gain-length product (DTGLP) increases up to 5. For tp = 1.0 ms, comparable modulation of the gain distribution is achieved for a much lower DTGLP value of 2.3. To extend the DTGLP range for long pump duration, a modified 1D iterative method with an effectively “shortened” lifetime of the active ions is developed. With the modified method, the gain uniformity for both pumping conditions is greatly improved, and specifically, the DTGLP increases from 2.3 to 3.0 for tp = 1.0 ms. In addition, degradation of the gain uniformity resulting from deviations of the doping concentration is discussed. The deviations should be at least lower than 1% and 5% for tp = 1.0 ms and tp = 0.25 ms to maintain the gain uniformity, respectively. Our investigations might provide a useful way to design the amplifier with uniform gain in the beam aperture of a high average power pulsed laser.