Theoretical and experimental investigations on sub-nanosecond KTP-OPO pumped by a hybrid Q-switched laser with AOM and MoTe2 saturable absorber

In this paper, few-layered molybdenum ditelluride (MoTe2) nanosheets are synthesized with a liquid-phase exfoliation method. Its appearance, the spectra and the saturated absorption characteristics are measured. By using MoTe2 as saturable absorber (SA), a passively Q-switched YVO4/Nd:YVO4 laser is realized. At an incident pump power of 6.64 W, a maximum output power of 1.14 W with a minimum pulse duration of 66.2 ns is obtained. To our knowledge, this is the shortest pulse width ever achieved from a passively Q-switched laser with a MoTe2-SA at 1.06 & mu;m. Based on this, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillation (IOPO) pumped by a hybrid Q-switched laser with a MoTe2-SA and an acousto-optic modulator (AOM) is realized. At an incident pump power of 10.4 W and an AOM repetition rate of 10 kHz, a maximum output power of 195 mW with a minimum pulse duration of 835 ps for signal wave is obtained. To solve the IOPO rate equations, the ground-state and excited-state absorption cross sections of MoTe2 are rationally calculated to be 1.32 x 10-18 cm2 and 9.15 x 10-19 cm2 according to the observed transmittance curve, respectively, and the excited-state lifetime is 376.2 & mu;s. The numerical solution of the equations matches well with the experimental data.

Automated summary

This paper synthesizes few-layered molybdenum ditelluride (MoTe2) nanosheets through liquid-phase exfoliation and measures their appearance, spectra, and saturated absorption characteristics. The MoTe2 is used as a saturable absorber (SA) to achieve a passively Q-switched YVO4/Nd:YVO4 laser with a maximum output power of 1.14 W and a minimum pulse duration of 66.2 ns. Moreover, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillation (IOPO) is realized using a hybrid Q-switched laser with a MoTe2-SA and an acousto-optic modulator (AOM), resulting in a maximum output power of 195 mW and a minimum pulse duration of 835 ps for the signal wave.