半导体薄膜实现Nd:YVO4 1064 nm和1342 nm双波长激光被动调Q

采用射频磁控溅射和热退火处理技术制备SiNx/Si/SiNx多层薄膜，测试了纳米硅晶粒平均尺寸、光学带隙和薄膜对1064 nm激光的非线性吸收系数。建立SiNx/Si/SiNx多层薄膜被动调Q的Nd:YVO4双波长激光器速率方程，得到双波长调Q脉冲的数值模拟结果。在激光二极管(LD)端面抽运的三镜复合腔Nd:YVO4激光器中，SiNx/Si/SiNx多层薄膜作为可饱和吸收体同时实现了双波长激光被动调Q，获得20 ns的1064 nm激光脉冲和19 ns的1342 nm激光脉冲输出。研究表明，薄膜对1064 nm和对1342 nm的双光子饱和吸收是双波长激光被动调Q的直接原因；激光器两个支腔输出损耗的差别和薄膜对两个波长的非线性吸收系数的相对值影响了双波长脉冲的宽度和时间间隔。

Semiconductor Film Passively Q-Switching for Dual-Wavelength Lasers at 1064 nm and 1342 nm in Nd:YVO4 Laser

The SiNx/Si/SiNx multi-layer film is prepared by radio-frequency magnetron sputtering and thermal annealing. The average grain size of nanocrystalline silicon, the optical band-gap and the nonlinear absorption coefficient at 1064 nm laser are characterized and estimated. The rate-equation theoretical model of the dual-wavelength laser passively Q-switched by SiNx/Si/SiNx multi-layer film is established and the dynamics of the dual-wavelength pulse formation is numerically calculated. Simultaneous dual-wavelength passive Q-switching is realized in a laser diode (LD) end-pumped three-mirror compound resonator Nd:YVO4 laser using SiNx/Si/SiNx film as the saturable absorber. Both 1064 nm pulse with 20 ns duration and 1342 nm pulse with 19 ns duration are obtained. The results show that dual-wavelength passive Q-switching mainly results from two-photon saturable absorptions for 1064 nm and 1342 nm lasers, and that the difference of output losses between the two overlapping collinear cavities and the relative nonlinear absorption coefficients for dual-wavelength lasers influence the pulse durations and time separation of dual-wavelength pulses.