@article{oai:tsukuba.repo.nii.ac.jp:00028088,
 author = {長谷, 宗明 and Hase, Muneaki and Katsuragawa, Masayuki and Constantinescu, Anca Monia and Petek, Hrvoje},
 issue = {4},
 journal = {Nature photonics},
 month = {Apr},
 note = {High-order nonlinear light–matter interactions in gases enable the generation of X-ray and attosecond light pulses, metrology and spectroscopy1. Optical nonlinearities in solid-state materials are particularly interesting for combining optical and electronic functions for high-bandwidth information processing2. Third-order nonlinear optical processes in silicon have been used to process optical signals with bandwidths greater than 1 GHz (ref. 2). However, fundamental physical processes for a silicon-based optical modulator in the terahertz bandwidth range have not yet been explored. Here, we demonstrate ultrafast phononic modulation of the optical index of silicon by irradiation with intense few-cycle femtosecond pulses. The anisotropic reflectivity modulation by the resonant Raman susceptibility at the fundamental frequency of the longitudinal optical phonon of silicon (15.6 THz) generates a frequency comb up to seventh order. All-optical >100 THz frequency comb generation is realized by harnessing the coherent atomic motion of the silicon crystalline lattice at its highest mechanical frequency.},
 pages = {243--247},
 title = {Frequency comb generation at terahertz frequencies by coherent phonon excitation in silicon},
 volume = {6},
 year = {2012}
}