太赫兹波段介质微腔光学特性研究

Optical properties of terahertz dielectric microcavity

采用匀胶法制备了厚度在微米量级的Si/[TiO2/Al2O3]2TiO2和Si/[TiO2/MgO]2/TiO2多层介质膜反射镜.采用太赫兹(THz)时域透射光谱系统获得了多层膜的时域透射谱.用传输矩阵法模拟了Si/[TiO2/Al2O3]2TiO2和Si/[TiO2/MgO]2/TiO2两种分布式布拉格反射镜(DBR)的反射相移和相位穿透深度等光学特性.设计了两种结构为DBR/LT-GaAs/DBR的对称THz光学微腔结构并模拟了腔结构的辐射光谱.结果表明:通过引入谐振腔,两种DBR组成的微腔器件在谐振波长处的强度分别提高了19和14倍.其中Si/[TiO2/Al2O3]2TiO2/LT-GaAs(12μm)/[TiO2/Al2O3]2TiO2腔的辐射光谱存在两个峰,分别位于208和248μm,并分析了出现两个谐振峰的原因.探讨了通过引入介质谐振腔实现对THz源的辐射特性进行调控的可行性.

In this paper, multilayer films Si/[TiO2/Al2O3 ]^2TiO 2 and Si/[TiO2/MgO]^2/TiO2 with thickness values from microns to tens of microns are fabricated by spin-coating method. The transmission spectra of these films are obtained by terahertz time-domain transmission spectrum system （THz-TDS）. The phase shifts of reflection and phase penetration depths of Si/[TiO2/Al2O3 ]^2TiO2 and Si/[TiO2/MgO]^2/TiO2 are simulated by the transfer matrix method. On this basis, two kinds of symmetrical THz microcavities each with a structure of DBR/LT-GaAs/DBR are designed and the radiation spectra are also simulated. The results show that the intensities of two microcavities are enhanced by 19 and 14 times at resonance wavelength, respectively. There are two resonance peaks in the emission spectrum of the structure Si/[TiO 2/Al2O3 ]^2TiO2 /LT-GaAs （12μm）/[TiO2/Al2O3]^2TiO2 , which are located at 208 μm and 248 μm, respectively. The reason is discussed based on the effective cavity length. The feasibility to regulate the emission properties of the THz source by introducing dielectric microcavities is discussed.