Coherent electromagnetic radiation is generated by the oscillation of longitudinal modes associated with optical phonons and bulk plasmons in InAs. Dramatic changes to the radiation spectra occur when the plasmon and phonon frequencies are in close spectral proximity, i.e., when the modes become strongly coupled.

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Far-infrared electromagnetic radiation is emitted by coherent plasmon oscillations in bulk (111) InSb. The oscillations are excited by near-infrared ultrashort laser pulses and characterized as a function of temperature. The coherent plasmon frequency is determined by the intrinsic electron concentration and donor doping density. The amplitude of the oscillations decreases with increasing temperature due to a weakening of the photo-Dember starting mechanism.

Electromagnetic radiation is emitted by the vibrational and collective modes of an opaque solid as the result of impulsive stimulated Raman scattering. Raman scattering of near-infrared femtosecond laser pulses produces coherent longitudinal optical phonon and plasmon oscillations in the semiconductor InSb. These oscillations radiate into free space at THz frequencies and are directly detected. The THz spectra exhibit features consistent with Raman selection rules including interference of allowed and forbidden Raman scattering.

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