Far-Infrared nonlinear response of electrons in semiconductor nanostructures

Electrons in semiconductor nanostructures such as quantum wells can exhibit a highly nonlinear response to far-infrared radiation of sufficient intensity, such as can be supplied by the free-electron lasers (FELs) at UCSB. Several different physical mechanisms can cause nonlinear behavior in nanostructures. Experimental results at UCSB demonstrate that transport, absorption, and harmonic generation can be used as probes of nonlinear response. In the future, it may be possible to use the UCSB-FELs to observe completely new nonlinear phenomena, such as non-perturbative quantum resonances in quantum wells driven by intense far-infrared radiation.