%0 Journal Article
%T Broadband THz absorption spectrometer based on excitonic nonlinear optical effects
%J -
%D 2019
%R https://doi.org/10.1038/s41377-019-0137-y
%X A broadly tunable THz source is realized via difference frequency generation, in which an enhancement to 聿(3) that is obtained via resonant excitation of III每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每i每n junction to produce effective 聿(2) processes, which are derived from the high 聿(3). This 聿(2) media exhibits an onset of nonlinear processes at ~4ˋWˋcmˋ2, thereby enabling area (and, hence, power) scaling of the THz emitter. Phase matching is realized laterally through normal incidence excitation. Using two collimated 130ˋmW continuous wave (CW) semiconductor lasers with ~1-mm beam diameters, we realize monochromatic THz emission that is tunable from 0.75 to 3ˋTHz and demonstrate the possibility that this may span 0.2每6ˋTHz with linewidths of ~20ˋGHz and efficiencies of ~1ˋ℅ˋ10每5, thereby realizing ~800ˋnW of THz power. Then, transmission spectroscopy of atmospheric features is demonstrated, thereby opening the way for compact, low-cost, swept-wavelength THz spectroscopy
%U https://www.nature.com/articles/s41377-019-0137-y