单层ITO薄膜在ENZ波段增强非线性光学效应的研究

Enhanced Nonlinear Optical Effects of Monolayer ITO Films in The Epsilon-Near-Zero Wavelength

摘要:

在玻璃基底上镀35nm厚的ITO薄膜,通过椭偏仪测量ITO薄膜的线性介电常数。由于ITO具有高掺杂浓度,因此其介电常数可以用Drude模型来进行量化计算,得到其介电常数近零(ENZ)波长约为λ=1100nm。借助双温模型计算电子温度和晶格温度随时间的变化,根据电子温度的升高计算等离子体频率的变化,将其带入Drude模型中,可以得到一个新的介电常数,最后可以通过计算折射率的变化,从而求出非线性折射率n₂。计算结果表明,在ENZ波长入射时,可以得到最大非线性折射率n₂=4.66×10-15m²/W。因此,实验中选取的材料可在低功率光照下得到显著的折射率变化,可望应用于全光存储、全光开关等纳米光子器件的设计。

Abstract:

The ITO film with the thickness of 35nm was plated on the glass substrate, and the linear permittivity of the ITO film was measured via spectroscopic ellipsometry. Owing to the large doping concentration of ITO, its permittivity can be quantified by Drude model, and the epsilon-near-zero wavelength is obtained as 1100nm. The varying rules of electronic temperature and lattice temperature with time can be calculated through the double-temperature model. The change of plasma frequency can be calculated with the increasing electronic temperature, and then it is taken into the Drude model to get a new permittivity. Finally, by calculating the variation of the refractive index, the nonlinear refractive index n₂ can be obtained. The calculated results show that the maximum nonlinear refractive index of n₂=4.66×10-15m²/W can be obtained at epsilon near zero wavelength. It is expected to apply in the nano photonic devices such as optical storage, all-optical switches and so on.