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采用射频磁控反应溅射技术与热退火处理制备了nc-Si/SiNx多量子阱材料。对样品进行了小角度XRD、Raman光谱、吸收光谱测试,研究了其结构和光学性质。采用皮秒脉冲激光单光束Z-扫描技术研究了样品在非共振吸收区的三阶非线性光学特性。实验结果表明,其非线性折射率为负值,非线性吸收属于双光子吸收。由实验数据计算得材料三阶非线性极化率为7.50×10-8esu,该值比体硅材料的三阶非线性极化率大4个数量级。对材料光学非线性产生的机理进行了探讨,认为材料的非线性极化率的增加来源于材料量子限制效应增强。
The nc-Si / SiNx multiple quantum well material was prepared by RF magnetron reactive sputtering and thermal annealing. The samples were examined by XRD, Raman spectroscopy and absorption spectroscopy. Their structures and optical properties were studied. The third-order nonlinear optical properties of the sample in the nonresonant absorption region were investigated using a picosecond pulsed laser single beam Z-scan technique. The experimental results show that the nonlinear refractive index is negative and the nonlinear absorption belongs to two-photon absorption. The third-order nonlinear polarizability of the material calculated from the experimental data is 7.50 × 10-8esu, which is 4 orders of magnitude larger than the third-order nonlinear polarizability of bulk silicon. The mechanism of optical nonlinearity of materials is discussed. It is considered that the increase of nonlinear polarizability of materials comes from the enhancement of material quantum confinement effect.