Diode-pumped passively Q-switched Nd:GdTaO4 laser based on tungsten disulfide nanosheets saturable absorber at 1066 nm
Introduction
In recent years, passively Q-switched laser with the pulse width from nanosecond to microsecond were of great significance on many respects such as scientific research, medical application, material processing, range finding, remote sensing and nonlinear frequency conversion [1]. In order to obtain highly compact laser system, native and foreign experts researched numerous saturable absorbers such as Cr4+:YAG [2], Cr2+:ZnSe [3], semiconductor saturable absorption mirror (SESAM) [4], single-walled carbon nanotubes [5]. To summarize, the saturable absorbers should have the advantages of high saturated-absorption characteristic, wavelength independence, high damage threshold, simple manufacturing process, low cost and so on. In the last few years, the two-dimensional (2D) nanosheets were widely used in the preparation of saturable absorbers. There were plenty of methods to obtain 2D nanosheets including chemical vapor deposition, mechanical exfoliation and liquid-phase exfoliation [6], [7], [8], [9], [10]. The liquid-phase exfoliation method was a practical and cost-effective way to manufacture 2D nanosheets. WS2 material demonstrated excellent saturable absorption property and high modulation depth at broadband wavelength, and WS2 saturable absorber was simple to prepare.
In this paper, we designed the LD diode-pumped passively Q-switched Nd:GdTaO4 laser based on WS2 saturable absorber. With the pump power of 4.5 W, we got two sets of data: (1) when the output coupling efficiency was 15%, the output power was 356 mW, the optical conversion efficiency was 7.91%, the pulse width was 608 ns, the repetition rate was 61.2 kHz; (2) when the output coupling efficiency was 10%, the output power was 309 mW, the optical conversion efficiency was 6.87%, the pulse width was 560 ns, the repetition rate was 70 kHz. The passively Q-switched Nd:GdTaO4 laser based on WS2 saturable absorber operated at a central wavelength of 1066 nm.
Section snippets
Preparation of WS2 saturable absorber
First of all, we added 0.02 g WS2 powder with a purity of 99.99% into 20 ml pure alcohol. Secondly, we agitated the solution through the centrifuge for 20 min. Thirdly, we placed a quartz substrate with the size of 25 mm × 10 mm into the solution. Then, we put the quartz substrate in the drying oven for 10 h in order to remove the alcohol thoroughly. Finally, the WS2 solution stably attached onto the quartz substrate.
Fig. 1 shows the transmitted spectrum of WS2 saturable absorber. The
Experimental setup
Fig. 3 shows the experimental setup of the LD diode-pumped Nd:GdTaO4 laser based on WS2 saturable absorber. The pumping source was the fiber-coupled diode laser with a central wavelength of 808 nm, the pump light coupled into the Nd:GdTaO4 crystal by the focus optics system. The Nd:GdTaO4 crystal was used as the gain medium with the dimensions of 3 × 3 × 5 mm3. The crystal was mounted in a water-cooled copper block, and the circulating water remained below 20 °C. M1 was a flat mirror (high
Conclusion
To summarize, a LD diode-pumped passively Q-switched Nd:GdTaO4 laser based on WS2 saturable absorber at 1066 nm was designed. With the pump power of 4.5 W, we got two sets of data: (1) with the output coupling efficiency of 15%, the output power was 356 mW, the optical conversion efficiency was 7.91%, the pulse width was 608 ns, the repetition rate was 61.2 kHz; (2) with the output coupling efficiency of 10%, the output power was 309 mW, the optical conversion efficiency was 6.87%, the pulse
Conflict of interest
The authors declare no conflict of interest.
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