应用于太赫兹探测器的宽带减反结构设计

Broadband Anti-Reflection Structure for Terahertz Detectors

摘要:

在太赫兹波段,高阻硅和蓝宝石具有低吸收率、高电阻率和低光谱色散等优良特性,常被用作器件的衬底材料。然而,它们的折射率与空气存在较大差异,导致从空气入射的太赫兹波在界面发生大量反射,从而降低了波的透过率；同时,还可能会引发法布里-珀罗谐振腔效应,进而限制太赫兹探测器的工作带宽和灵敏度。为降低界面反射,文章提出一种太赫兹波段的三层减反射结构,借助Matlab中传输矩阵法和电磁场仿真中有限元法进行仿真,筛选出Mylar/Al₂O₃/AlN的材料组合。仿真结果表明,在340GHz的入射波照射下,该结构在275~405GHz范围内反射率均低于-20dB,将其应用于太赫兹探测器后,-3dB带宽提升至50GHz以上,响应度提高了3.2倍。该结构制备简单、成本低廉,为太赫兹波段的宽带减反提供了一种经济且有效的解决方案。

Abstract:

In the terahertz band, high-resistivity silicon and sapphire are commonly used as substrates for terahertz devices owing to their low absorption, high resistivity, and low spectral dispersion. However, the high refractive index results in most of the incident terahertz waves being reflected at the interface, leading to a reduced wave transmittance and a potential Fabry-Perot resonant cavity effect, limiting the operating bandwidth and sensitivity of the terahertz device. To reduce the reflection of terahertz waves at the interface, this study proposes a three-layer anti-reflection structure. By using the transfer matrix method (TMM) in MATLAB and the finite-difference method in the time-domain (FDTD) in electromagnetic simulation, Mylar/Al₂O₃/AlN is selected as the anti-reflection structure in the terahertz range. The simulation results show that this structure can maintain a reflectivity ＜-20dB in the range of 275~405GHz. Furthermore, the terahertz detector applying this anti-reflection structure exhibits a -3dB bandwidth enhancement of ＞50GHz and a 3.2-fold increase in responsivity at 340GHz. Additionally, the structure has a straightforward and cost-effective fabrication process, providing an economical and effective solution for broadband reflection reduction in the terahertz band.