Broadband THz absorption spectrometer based on excitonic nonlinear optical effects

Avan Majeed, Pavlo Ivanov, Benjamin Stevens, Edmund Clarke, Iain Butler, David Childs, Osamu Kojima, Richard Hogg*

*Corresponding author for this work

Research output: Contribution to journalLetterpeer-review

8 Citations (Scopus)
54 Downloads (Pure)


A broadly tunable THz source is realized via difference frequency generation, in which an enhancement to χ(3) that is obtained via resonant excitation of III–V semiconductor quantum well excitons is utilized. The symmetry of the quantum wells (QWs) is broken by utilizing the built-in electric-field across a p–i–n junction to produce effective χ(2) processes, which are derived from the high χ(3). This χ(2) media exhibits an onset of nonlinear processes at ~4 W cm−2, thereby enabling area (and, hence, power) scaling of the THz emitter. Phase matching is realized laterally through normal incidence excitation. Using two collimated 130 mW continuous wave (CW) semiconductor lasers with ~1-mm beam diameters, we realize monochromatic THz emission that is tunable from 0.75 to 3 THz and demonstrate the possibility that this may span 0.2–6 THz with linewidths of ~20 GHz and efficiencies of ~1 × 10–5, thereby realizing ~800 nW of THz power. Then, transmission spectroscopy of atmospheric features is demonstrated, thereby opening the way for compact, low-cost, swept-wavelength THz spectroscopy.

Original languageEnglish
Article number29
JournalLight: Science and Applications
Issue number1
Publication statusPublished - 13 Mar 2019

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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