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

Abstract

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.

Passive Q-Switching by Cr4+:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing

“…A monolayer of graphene was coated for Q-switch operation on the exit surface of a two-track Yb:YAG waveguide [ 21 ] and a circular depressed-cladding waveguide inscribed in Ho:YAG was operated at 2.1 μm in Q-switch mode-locking regime with a graphene based saturable output coupler [ 22 ]. Among other recent results we can mention the following: carbon nanotubes were used to obtain Q-switched laser emission from a channel waveguide inscribed in Yb:YAG [ 23 ]; a circular depressed-cladding waveguide inscribed in Nd:YAG was operated in Q-switch regime by MoS 2 SA [ 24 ], as well as with molybdenum diselenide and tungsten diselenide membranes covered on silica wafers [ 25 ]; vanadium dioxide was investigated for Q-switch operation in depressed-cladding waveguides inscribed in Nd:YVO 4 [ 26 ]. The use of such SA materials [ 23 , 24 , 25 ] resulted, however, in Q-switch laser operation with low pulse energy, of a few tens up to about one hundred nJ and long duration, from tens of ns up to several hundred ns.…”

Passive Q-switch laser operation of circular, buried depressed-cladding waveguides realized by direct fs-laser beam writing in Nd:YAG/Cr^4+:YAG composite media

“…The laser operated at f p = 5.4 MHz yielding pulses with duration t p = 11 ns and energy E p ∼1 μJ. A VO 2 SA crystal was used to Q-switch superficial cladding waveguides that were inscribed in Nd:YVO 4 [33]. Laser pulses with t p = 690 ps were obtained at f p = 2.9 MHz; the average power was P ave = 66.7 mW, indicating that energy E p was around 23 nJ.…”

Investigation of structural mechanisms of laser-written waveguide formation through third-harmonic microscopy

“…By virtue of its rapid prototyping nature and compatibility with different materials, femtosecond-laser direct writing has become a popular fabrication technology for photonic integrated circuits (PICs) for photon-based quantum information processing (QIP) [1][2][3][4][5][6][7][8] among other application areas [9][10][11][12][13][14][15][16][17]. In particular, its intrinsic three-dimensional (3D) fabrication capability uniquely enables the fabrication of PICs involving complex 3D photonic structures [18][19][20][21].…”