Self-phase modulation and nonlinear loss in silicon nanophotonic wires near the mid-infrared two-photon absorption edge.
Self-phase modulation and nonlinear loss in silicon nanophotonic wires near the mid-infrared two-photon absorption edge.
复制标题
DOI：
10.1364/oe.19.007778
复制
发表时间：
2011-04
期刊：
影响因子：
3.8
通讯作者：
Xiaoping Liu;J. Driscoll;J. Dadap;R. Osgood;S. Assefa;Y. Vlasov;W. Green
中科院分区：
文献类型：
--
作者：
Xiaoping Liu;J. Driscoll;J. Dadap;R. Osgood;S. Assefa;Y. Vlasov;W. Green
我们报道了皮秒脉冲在1775 ~ 2250 nm激发波长范围内通过4 mm长正常色散的Si纳米光子线的实验研究。该波长范围在~2200 nm处穿过Si的中红外双光子吸收边缘。当激发波长接近2200 nm时，由于双光子吸收，非线性损耗显著降低。在高输入功率下，自相位调制通过功率相关谱条纹的发展得到了清晰的证明。光谱条纹在1775 nm和2200 nm处的不对称性和蓝移进一步表明是由于双光子吸收产生的自由载流子的脉冲内密度和相关的自由载流子色散的强烈减少。实验数据分析和数值模拟对比表明，通过纳米光子线测量得到的双光子吸收系数β(TPA)与先前块状硅晶体的测量结果基本一致，并且块状硅的非线性折射率n(2)值可以自信地纳入深尺度波导结构中脉冲传播的建模中。
We report an experimental study of picosecond pulse propagation through a 4-mm-long Si nanophotonic wire with normal dispersion, at excitation wavelengths from 1775 to 2250 nm. This wavelength range crosses the mid-infrared two-photon absorption edge of Si at ~2200 nm. Significant reduction in nonlinear loss due to two-photon absorption is measured as excitation wavelengths approach 2200 nm. At high input power, self-phase modulation is clearly demonstrated by the development of power-dependant spectral fringes. Asymmetry and blue-shift in the appearance of the spectral fringes at 1775 nm versus 2200 nm is further shown to originate from a strong reduction in the intra-pulse density of two-photon absorption-generated free carriers and the associated free-carrier dispersion. Analysis of experimental data and comparison with numerical simulations illustrates that the two-photon absorption coefficient β(TPA) obtained here from nanophotonic wire measurements is in reasonable agreement with prior measurements of bulk silicon crystals, and that bulk Si values of the nonlinear refractive index n(2) can be confidently incorporated in the modeling of pulse propagation in deeply-scaled waveguide structures.