1202.5153 (Dmitry Turchinovich et al.)

Self-phase modulation of a single-cycle terahertz pulse by nonlinear
free-carrier response in a semiconductor    [PDF]

Dmitry Turchinovich, Jørn M. Hvam, Matthias C. Hoffmann

We demonstrate the self-phase modulation (SPM) of a single-cycle THz pulse in
a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the
heating of free electrons in the electric field of the THz pulse, leading to an
ultrafast reduction of the plasma frequency, and hence to a strong modification
of the THz-range dielectric function of the material. THz SPM is observed
directly in the time domain. In the frequency domain it corresponds to a strong
frequency-dependent refractive index nonlinearity of n-GaAs, found to be both
positive and negative within the broad THz pulse spectrum, with the
zero-crossing point defined by the electron momentum relaxation rate. We also
observed the nonlinear spectral broadening and compression of the THz pulse.

View original: http://arxiv.org/abs/1202.5153