Broadband THz absorption spectrometer based on excitonic nonlinear optical effects.

ABSTRACT: A broadly tunable THz source is realized via difference frequency generation, in which an enhancement to ?(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 ?(2) processes, which are derived from the high ?(3). This ?(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.

SUBMITTER: Majeed A 

PROVIDER: S-EPMC6414654 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature