Ultrafast opto-terahertz photonic crystal modulator

We present an agile optically controlled switch or modulator of terahertz (THz) radiation. The element is based on a one-dimensional photonic crystal with a GaAs wafer inserted in the middle as a defect layer. The THz electric field is enhanced in the photonic structure at the surfaces of the Ga-As wafer. Excitation of the front GaAs surface by ultrashort 8 10 nm laser pulses then leads to an efficient modulation of the THz beam even at low photocarrier concentrations (approximate to 10(16) cm(-3)). The response time of the element to pulsed photoexcitation is about 130 ps. (c) 2007 Optical Society of America.