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Room-temperature subnanosecond waveguide lasers in Nd:YVO 4 Q-switched by phase-change VO 2 : A comparison with 2D materials

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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.

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The average output power of pulsed laser with different SAs.The average output power at 1064 nm as a function of launched pump power in pulsed regime with SAMs of VO2 (red line), graphene (blue line) and WS2 (green line) along (a) TE and (b) TM polarization, respectively.
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f3: The average output power of pulsed laser with different SAs.The average output power at 1064 nm as a function of launched pump power in pulsed regime with SAMs of VO2 (red line), graphene (blue line) and WS2 (green line) along (a) TE and (b) TM polarization, respectively.

Mentions: Figures 3(a) and (b) show the average output powers at 1064 nm as a function of launched pump power in pulsed regime with three different SAMs along TE and TM polarization, respectively. The fitted straight lines with the color of red, blue and green denote the pulse laser performance with VO2, graphene, and WS2 SAMs, separately. For TE polarization (Fig. 3(a)), the pulsed waveguide laser oscillation begins with VO2, graphene, and WS2 SAMs when the launched power exceeds the lasing thresholds of 18.8, 86.1 and 30.3 mW, respectively. The slope efficiencies of 6.2%, 14.2% and 15.2% have been obtained from the linear fit of experiment data, respectively. As the pump power rises linearly to the maximum of 1006.2 mW, the output power of the pulsed waveguide laser reaches the maximum value of 66.7, 152.2 and 161.9 mW, respectively. Whilst for TM polarization (see Fig. 3(b)), the lasing thresholds measured in the experiment are 22.7, 90.8 and 53.0 mW in the VO2, graphene, and WS2 based systems, respectively. By the increase of launched power from the lasing threshold to the maximum value of 1006.2 mW, the Q-switching operates pulsed lasers with the maximum output power of 58.8, 136.8 and 141.1 mW and slope efficiencies of 5.9%, 12.8% and 14.6% for the three different SAMs, separately. According to Fig. 3, one could conclude that the pulsed waveguide laser performance in terms of lasing threshold, slope efficiency and maximum output laser at TE polarization is better than those at TM polarization for all of them. This may be partly due to the polarization properties on guidance of the superficial cladding waveguide in Nd:YVO4 crystal (Fig. 2). In addition, as one can see, with the phase-change material of VO2, the lasing threshold of the pulsed laser is much lower in comparison to those based on 2D materials. This is in good agreement with the Nd3+ doped vanadate bulk laser systems44. Under this condition, it becomes more easily to realize the pulsed laser generation with low intra-cavity intensity, indicating the sensitive nonlinear responses and revealing the promising application in optoelectronic sensors4650. Moreover, in the aspect of maximum output power and slope efficiency, Q-switched waveguide laser with WS2 SAM has the highest value among three nanomaterials based systems, which is still feasible to reach higher-power output by increasing the pump power. For VO2, the phase-change material, it may be transferred from pulsed regime to CW operation as the temperature of the system exceeds the VO2 phase transition point due to the high-power laser induced heating effect45.


Room-temperature subnanosecond waveguide lasers in Nd:YVO 4 Q-switched by phase-change VO 2 : A comparison with 2D materials
The average output power of pulsed laser with different SAs.The average output power at 1064 nm as a function of launched pump power in pulsed regime with SAMs of VO2 (red line), graphene (blue line) and WS2 (green line) along (a) TE and (b) TM polarization, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382777&req=5

f3: The average output power of pulsed laser with different SAs.The average output power at 1064 nm as a function of launched pump power in pulsed regime with SAMs of VO2 (red line), graphene (blue line) and WS2 (green line) along (a) TE and (b) TM polarization, respectively.
Mentions: Figures 3(a) and (b) show the average output powers at 1064 nm as a function of launched pump power in pulsed regime with three different SAMs along TE and TM polarization, respectively. The fitted straight lines with the color of red, blue and green denote the pulse laser performance with VO2, graphene, and WS2 SAMs, separately. For TE polarization (Fig. 3(a)), the pulsed waveguide laser oscillation begins with VO2, graphene, and WS2 SAMs when the launched power exceeds the lasing thresholds of 18.8, 86.1 and 30.3 mW, respectively. The slope efficiencies of 6.2%, 14.2% and 15.2% have been obtained from the linear fit of experiment data, respectively. As the pump power rises linearly to the maximum of 1006.2 mW, the output power of the pulsed waveguide laser reaches the maximum value of 66.7, 152.2 and 161.9 mW, respectively. Whilst for TM polarization (see Fig. 3(b)), the lasing thresholds measured in the experiment are 22.7, 90.8 and 53.0 mW in the VO2, graphene, and WS2 based systems, respectively. By the increase of launched power from the lasing threshold to the maximum value of 1006.2 mW, the Q-switching operates pulsed lasers with the maximum output power of 58.8, 136.8 and 141.1 mW and slope efficiencies of 5.9%, 12.8% and 14.6% for the three different SAMs, separately. According to Fig. 3, one could conclude that the pulsed waveguide laser performance in terms of lasing threshold, slope efficiency and maximum output laser at TE polarization is better than those at TM polarization for all of them. This may be partly due to the polarization properties on guidance of the superficial cladding waveguide in Nd:YVO4 crystal (Fig. 2). In addition, as one can see, with the phase-change material of VO2, the lasing threshold of the pulsed laser is much lower in comparison to those based on 2D materials. This is in good agreement with the Nd3+ doped vanadate bulk laser systems44. Under this condition, it becomes more easily to realize the pulsed laser generation with low intra-cavity intensity, indicating the sensitive nonlinear responses and revealing the promising application in optoelectronic sensors4650. Moreover, in the aspect of maximum output power and slope efficiency, Q-switched waveguide laser with WS2 SAM has the highest value among three nanomaterials based systems, which is still feasible to reach higher-power output by increasing the pump power. For VO2, the phase-change material, it may be transferred from pulsed regime to CW operation as the temperature of the system exceeds the VO2 phase transition point due to the high-power laser induced heating effect45.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus