Preliminary Experiment on Direct Media Conversion from a 1.55 µm Optical Signal to a Sub-Terahertz Wave Signal Using Photon-Generated Free Carriers

A novel method of direct media conversion from an optical signal to a terahertz (THz) signal using free carriers generated by photons and the skin effect is proposed. A semiconductor modulator absorbs modulated optical signals and generates free carriers. These free carriers inside the modulator absorb THz waves owing to the skin effect, thereby creating an inverted pattern signal of the THz wave with respect to the optical signal. In preliminary experiments using 192 GHz continuous waves and a 1.55 µm optical signal, a modulation depth of 45% and a modulation speed of up to 1 MHz were demonstrated.