We demonstrate a nanoscale, subpicosecond (ps) metamaterial device capable of terabit/second all-optical communication in the near-IR. The 600 fs response, 2 orders of magnitude faster than previously reported, is achieved by accessing a previously unused regime of high-injection level, subpicosecond carrier dynamics in the α-Si dielectric layer of the metamaterial. Further, we utilize a previously unrecognized, higher-order, shorter-wavelength negative-index resonance in the fishnet structure, thereby extending device functionality (via structural tuning of device dimensions) over 1.0−2.0 μm. The pump energy required to modulate a single bit is only 3 nJ over our current 700 μm2 area device and can be easily scaled into the picoJoule regime with smaller cross sectional areas.

Terahertz time-domain spectroscopy has been used to measure the vibrational spectra of polycrystalline purine and adenine over the temperature range 4–290 K. A number of well-resolved absorption peaks were observed in the frequency range 0.2–3.0 THz, which are interpreted as originating from intermolecular vibrational modes mediated by hydrogen bonds. We find that as the temperature is reduced, the observed absorption bands resolve into narrower peaks and some shift towards higher frequencies. We explain the temperature dependence of the spectra by the anharmonicity of the vibrational potentials and give an empirical expression to describe the frequency shift.

Terahertz radiation was generated with a biased and asymmetrically excited low-temperature-grown GaAs photoconductive emitter, and characterized with a 20-μm-thick ZnTe crystal using free-space electro-optic sampling. Using a backward collection scheme, we obtained terahertz radiation with frequency components over 30 THz, the highest ever observed for photoconductive emitters. We present spectra over the whole frequency range between 0.3 and 20 THz, demonstrating the use of this source for ultrabroadband THz spectroscopy.