Ponderomotive potential effects in semiconductors

Summary form only given. We have observed induced absorption below the band edge and optical sideband generation in semiconductors strongly driven by intense mid-infrared (MIR) pulses. Phenomena of this type occur in matter when the applied electromagnetic field has a ponderomotive potential, U/sub p/=(2/spl pi/e/sup 2//mc)(I//spl omega//sup 2/), comparable to or greater than the photon energy, /spl planck//spl omega/. Matter in the presence of such strong electromagnetic fields exhibit properties that cannot be described by perturbation theory We have observed evidence of ponderomotive potential effects in strongly driven semiconductors: induced absorption below the band edge and the generation of multiple off-resonance optical sidebands. The optical sideband generation may be used as a means of characterizing MIR pulse duration and wavelength using near-infrared detectors, which are more sensitive than MIR detectors.