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

http://prb.aps.org/abstract/PRB/v85/i20/e201304
Dmitry Turchinovich^1,2,*, Jørn M. Hvam¹, and Matthias C. Hoffmann^3 
1DTU Fotonik, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
²Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
³SLAC Linear Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA

 Received 23 January 2012; published 29 May 2012

We investigate the self-phase modulation (SPM) of a single-cycle terahertz 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 terahertz pulse, leading to an ultrafast reduction of the plasma frequency, and hence to a strong modification of the terahertz-range dielectric function of the material. Terahertz 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 spectrum of the terahertz pulse, with the zero-nonlinearity point defined by the electron momentum relaxation rate. We also observed the nonlinear spectral broadening and compression of the terahertz pulse.

©2012 American Physical Society

URL:

http://link.aps.org/doi/10.1103/PhysRevB.85.201304

DOI:

10.1103/PhysRevB.85.201304

PACS:

78.20.-e, 42.65.Re, 72.20.Ht, 78.47.J-

^*dmtu@fotonik.dtu.dk