Increase in terahertz-wave intensity in a magnetic field due to difference-frequency mixing by exciton excitation in a GaAs/AlAs multiple quantum well.

Magnetic fields can increase the intensity of terahertz (THz) waves due to changing the dipole moment direction using the Lorentz force. This study reports the increase in the THz-wave intensity generated by differential frequency mixing using commercial permanent magnets under exciton-excitation. While a weak magnetic field applied to a multiple quantum well increases the THz-wave intensity due to excitons, a strong field causes its decrease.

Broadband THz absorption spectrometer based on excitonic nonlinear optical effects.

A broadly tunable THz source is realized via difference frequency generation, in which an enhancement to χ 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 processes, which are derived from the high χ. This χ media exhibits an onset of nonlinear processes at ~4 W cm, thereby enabling area (and, hence, power) scaling of the THz emitter.