60 nanotimes News in Brief

Dmitry Turchinovich (DTU Fotonik, Denmark, and Max Planck Institute for Polymer Research, Germany), Jørn M. Hvam (DTU), and Matthias C. Hoffmann (SLAC Linear Accelerator Laboratory, USA) have recently reported on the direct observation of a nonlinear-optical effect, occurring in the regime of single-cycle pulse of light at terahertz (THz) frequencies. They used a doped semiconductor as an efficient nonlinear medium, where the THz-range optical nonlinearity arises from the response of free-electron plasma to THz electric fields. One of the discoveries in this work was the coexistence of both positive and negative refractive index nonlinearity within the broad spectrum of a single-cycle THz pulse. 

Dmitry Turchinovich, Jørn M. Hvam, and Matthias C. Hoffmann: Self-phase modulation of a single-cycle terahertz pulse by nonlinear free-carrier response in a semiconductor, In: Physical Review B, Volume 85, Issue 20, May 15, 2012, Article 201304 [5 pages], DOI: 10.1103/PhysRevB.85.201304

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