Abstract-Low power ultra-broadband terahertz sideband generation in bilayer graphene

J. A. Crosse, Xiaodong Xu, Mark S. Sherwin, R. B. Liu

(Submitted on 6 Jan 2014)

http://arxiv.org/abs/1401.1055

In a semiconductor, an electron-hole pair, created by a weak optical laser and accelerated by an intense terahertz (THz) field, can recombine to emit light in a broad frequency comb evenly spaced by twice the THz frequency. Such high-order THz sideband generation (HSG) is of fundamental interest as an example of extreme nonlinear optics, and also of technological importance as in Tbit/sec optical communication. However, a broad HSG spectrum requires intense THz fields that are only available through large scale installations such as free-electron lasers, which precludes the practical use of HSG. Here we report on the discovery that a THz field of strength 1 kV/cm can produce an HSG spectrum of about 30 THz, 100 times broader than in GaAs (or, equivalently, a comparable bandwidth in GaAs would require THz field intensities 100 times stronger). These remarkable features enable desktop electro-optical modulation at THz frequencies, facilitating ultrafast optical communications.