TY - JOUR
T1 - Tunable cavity-enhanced terahertz frequency-domain optical Hall effect
AU - Knight, Sean
AU - Schöche, Stefan
AU - Kühne, Philipp
AU - Hofmann, Tino
AU - Darakchieva, Vanya
AU - Schubert, Mathias
N1 - Funding Information:
The authors thank Dr. Craig M. Herzinger for helpful discussions. Professor Nikolas Grandjean is gratefully acknowledged for providing the AlInN/GaN HEMT structure. The authors thank Dr. Chamseddine Bouhafs and Dr. Vallery Stanishev for growing the graphene sample and Professor Rositsa Yakimova for providing access to her sublimation facility for graphene growth. This work was supported in part by the National Science Foundation under Award No. DMR 1808715, the Air Force Office of Scientific Research under Award No. FA9550-18-1-0360, the Knut and Alice Wallenbergs Foundation supported grant “Wide-bandgap semiconductors for next generation quantum components,” the Swedish Agency for Innovation Systems under the Competence Center Program (Nos. 2016-05190 and 2014-04712), the Swedish Foundation for Strategic Research (Nos. RFI14-055 and EM16-0024), the Swedish Research Council (No. 2016-00889), the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO Mat LiU No. 2009 00971), and the J. A. Woollam Foundation.
PY - 2020/8/1
Y1 - 2020/8/1
N2 - 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.
AB - 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.
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U2 - 10.1063/5.0010267
DO - 10.1063/5.0010267
M3 - Article
C2 - 32872950
AN - SCOPUS:85090109497
VL - 91
JO - Review of Scientific Instruments
JF - Review of Scientific Instruments
SN - 0034-6748
IS - 8
M1 - 083903
ER -