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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
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Probing THz intersubband absorption using Johnson noise thermometry.

Changyun Yoo1, Mark S Sherwin2, Kenneth W West3

  • 1Jet Propulsiton Laboratory, California Institute of Technology, Pasadena, CA, USA.

Nanophotonics (Berlin, Germany)
|December 5, 2024
PubMed
Summary

We used Johnson noise thermometry to study terahertz (THz) intersubband absorption in a GaAs/AlGaAs quantum well. This method precisely measures electron heating and absorption in mesoscopic devices.

Keywords:
Johnson noise thermometryTHz intersubband transitionsTunable Antenna-Coupled Intersubband Terahertz (TACIT) mixer

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Area of Science:

  • Semiconductor physics
  • Quantum well devices
  • Terahertz spectroscopy

Background:

  • Intersubband absorption in quantum wells is crucial for THz optoelectronics.
  • Characterizing absorption in mesoscopic systems presents unique challenges.
  • Johnson noise thermometry offers a sensitive method for probing electronic properties.

Purpose of the Study:

  • To investigate THz intersubband absorption in a single GaAs/AlGaAs quantum well.
  • To utilize Johnson noise thermometry for precise measurements in mesoscopic devices.
  • To directly measure electron heating effects due to THz absorption.

Main Methods:

  • Fabrication of a single 40-nm wide GaAs/AlGaAs square quantum well.
  • Measurement of Johnson noise in the conduction channel under varying charge density and electric fields.
  • Application of monochromatic THz radiation at 2.52 THz and 4.25 THz at 20 K.
  • Modeling THz coupling efficiency using an impedance model.

Main Results:

  • Observed Johnson noise behavior correlates well with expected intersubband absorption.
  • The impedance model qualitatively reproduces the experimental Johnson noise.
  • Direct measurement of electron heating (ΔT) achieved during THz absorption.

Conclusions:

  • Johnson noise thermometry is effective for studying THz intersubband absorption in single quantum wells.
  • The study provides insights into electron heating mechanisms in mesoscopic semiconductor devices.
  • This technique enables the characterization of THz absorption in systems with a small number of electrons.