PMID- 32872950
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20200902
IS  - 1089-7623 (Electronic)
IS  - 0034-6748 (Linking)
VI  - 91
IP  - 8
DP  - 2020 Aug 1
TI  - Tunable cavity-enhanced terahertz frequency-domain optical Hall effect.
PG  - 083903
LID - 10.1063/5.0010267 [doi]
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-Perot 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.
FAU - Knight, Sean
AU  - Knight S
AUID- ORCID: 0000000227586967
AD  - Department of Electrical and Computer Engineering, University of 
      Nebraska-Lincoln, Lincoln, Nebraska 68588-0511, USA.
FAU - Schoche, Stefan
AU  - Schoche S
AD  - J. A. Woollam Co., Inc., Lincoln, Nebraska 68508-2243, USA.
FAU - Kuhne, Philipp
AU  - Kuhne P
AUID- ORCID: 0000000288277404
AD  - Terahertz Materials Analysis Center, THeMAC and Center for III-Nitride 
      Technology, C3NiT-Janzen, Department of Physics, Chemistry and Biology, Linkoping 
      University, SE 58183 Linkoping, Sweden.
FAU - Hofmann, Tino
AU  - Hofmann T
AUID- ORCID: 0000000333629959
AD  - Department of Physics and Optical Science, University of North Carolina at 
      Charlotte, Charlotte, North Carolina 28223, USA.
FAU - Darakchieva, Vanya
AU  - Darakchieva V
AUID- ORCID: 0000000281127411
AD  - Terahertz Materials Analysis Center, THeMAC and Center for III-Nitride 
      Technology, C3NiT-Janzen, Department of Physics, Chemistry and Biology, Linkoping 
      University, SE 58183 Linkoping, Sweden.
FAU - Schubert, Mathias
AU  - Schubert M
AUID- ORCID: 000000016238663X
AD  - Department of Electrical and Computer Engineering, University of 
      Nebraska-Lincoln, Lincoln, Nebraska 68588-0511, USA.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Rev Sci Instrum
JT  - The Review of scientific instruments
JID - 0405571
SB  - IM
EDAT- 2020/09/03 06:00
MHDA- 2020/09/03 06:01
CRDT- 2020/09/03 06:00
PHST- 2020/09/03 06:00 [entrez]
PHST- 2020/09/03 06:00 [pubmed]
PHST- 2020/09/03 06:01 [medline]
AID - 10.1063/5.0010267 [doi]
PST - ppublish
SO  - Rev Sci Instrum. 2020 Aug 1;91(8):083903. doi: 10.1063/5.0010267.