Room-temperature subnanosecond waveguide lasers in Nd:YVO₄ Q-switched by phase-change VO₂: A comparison with 2D...

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO₄ crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO₂). The unique feature of VO₂ nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO₄ waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO₂ saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS₂) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO₂ as low-cost saturable absorber for subnanosecond laser generation.