BN as a Saturable Absorber for a Passively Mode‐Locked 2 µm Solid‐State Laser

Abstract

Boron nitride (BN) nanosheets are prepared using an ultrasonic decomposition method and demonstrated nonlinear absorption characteristics that saturated at near 2 µm. A passively mode‐locked Tm:YAP laser was perfectly implemented with the BN nanosheets as a saturable absorber (SA). In the passively Q‐switched mode‐locked mode, an average output power of 880 mW with a pulse duration of 478.83 ps was achieved using an incident pump power of 26.46 W, corresponding to an optical–optical conversion efficiency of 3.33%. A pulse peak power of 19.03 W was acquired at 1937.0 nm from the mode‐locked Tm:YAP laser.