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Tunable cavity-enhanced terahertz frequency-domain optical Hall effect
Review of Scientific Instruments ( IF 1.6 ) Pub Date : 2020-08-01 , DOI: 10.1063/5.0010267
Sean Knight 1 , Stefan Schöche 2 , Philipp Kühne 3 , Tino Hofmann 4 , Vanya Darakchieva 3 , Mathias Schubert 1
Affiliation  

Presented here is the development and demonstration of a tunable cavity-enhanced terahertz (THz) frequency-domain optical Hall effect (OHE) technique. The cavity consists of at least one fixed and one tunable Fabry-Pérot resonator. The approach is suitable for the enhancement of the optical signatures produced by the OHE in semi-transparent conductive layer structures with plane parallel interfaces. Tuning one of the cavity parameters, such as the external cavity thickness, permits shifting of the frequencies of the constructive interference and provides substantial enhancement of the optical signatures produced by the OHE. A cavity-tuning optical stage and gas flow cell are used as examples of instruments that exploit tuning an external cavity to enhance polarization changes in a reflected THz beam. Permanent magnets are used to provide the necessary external magnetic field. Conveniently, the highly reflective surface of a permanent magnet can be used to create the tunable external cavity. The signal enhancement allows the extraction of the free charge carrier properties of thin films and can eliminate the need for expensive superconducting magnets. Furthermore, the thickness of the external cavity establishes an additional independent measurement condition, similar to, for example, the magnetic field strength, THz frequency, and angle of incidence. A high electron mobility transistor (HEMT) structure and epitaxial graphene are studied as examples. The tunable cavity-enhancement effect provides a maximum increase of more than one order of magnitude in the change of certain polarization components for both the HEMT structure and epitaxial graphene at particular frequencies and external cavity sizes.

中文翻译:

可调谐腔增强太赫兹频域光学霍尔效应

这里介绍的是可调谐腔增强太赫兹 (THz) 频域光学霍尔效应 (OHE) 技术的开发和演示。腔体由至少一个固定和一个可调法布里-珀罗谐振器组成。该方法适用于增强具有平面平行界面的半透明导电层结构中由 OHE 产生的光学特征。调整腔参数之一,例如外腔厚度,允许相长干涉的频率移动,并提供由 OHE 产生的光学特征的显着增强。腔调谐光学平台和气流池被用作利用调谐外腔来增强反射太赫兹光束的偏振变化的仪器的例子。永磁体用于提供必要的外部磁场。方便的是,永磁体的高反射表面可用于创建可调外腔。信号增强允许提取薄膜的自由电荷载流子特性,并且可以消除对昂贵的超导磁体的需要。此外,外腔的厚度建立了一个额外的独立测量条件,类似于例如磁场强度、太赫兹频率和入射角。以高电子迁移率晶体管 (HEMT) 结构和外延石墨烯为例进行了研究。
更新日期:2020-08-01
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