Evanescent-field Q-switched Yb:YAG Channel Waveguide Lasers with Single- and Double-pass Pumping

Abstract

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.