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采用射频磁控溅射技术和热退火处理技术制备了石英衬底的纳米Si镶嵌SiNx薄膜(nc-Si-SiNx),薄膜厚度为200 nm.由X射线衍射(XRD)谱计算得出,经800℃连续3 h退火的薄膜中的Si晶粒平均尺寸为1.7 nm.把纳米Si镶嵌SiNx薄膜作为可饱和吸收体插入闪光灯抽运的平凹腔Nd∶YAG激光器内,实现1.06μm激光的被动锁模运转.当激光器腔长为120 cm时,获得平均脉冲宽度32 ps,输出能量25 mJ的单脉冲序列,脉冲序列的包络时间约480 ns,锁模调制深度接近100%.量子限域效应使得纳米Si的能隙宽度大于1.06μm光子能量,所以双光子饱和吸收和光生载流子的快速能量弛豫是导致纳米Si镶嵌SiNx薄膜实现1.06μm激光被动锁模的主要原因.
A SiNx thin film (nc-Si-SiNx) with a thickness of 200 nm was prepared by radio-frequency magnetron sputtering and thermal annealing techniques. The X-ray diffraction (XRD) The average size of Si grains in the films annealed at 800 ℃ for 3 h was 1.7 nm.The nanosized SiNx thin films as saturable absorbers were inserted into flash-pumped flat-cavity Nd:YAG lasers to achieve 1.06 μm laser passivity When the laser cavity length is 120 cm, the average pulse width is 32 ps and the output pulse energy is 25 mJ. The envelope time of the pulse sequence is about 480 ns and the mode-locked depth is close to 100% Effect makes the energy gap width of nano-Si larger than 1.06μm photon energy, so the two-photon saturation absorption and photogenerated carrier fast energy relaxation is the main reason for the SiNx Si nano-Si film to achieve 1.06μm laser passive mode-locking.