Papers by Author: Tadao Tanabe

Abstract: An efficient continuous wave (CW) THz source working at nominal room temperature is described. Optically pumped room temperature THz emission is observed from various kinds of semiconductor bulk crystals. In order to investigate the emission mechanism, temperature dependences of terahertz emission intensity in various semiconductors are measured. Semiconductor samples used are InSb, InSb:Ge, InAs, GaSb, Ge, and Si. From these results, it is shown that the temperature dependences of emission characteristics are different between direct and indirect transition semiconductors, and that the high resistive Ge is suitable for room temperature THz emitter via intracenter transitions excited by IR pump lasers.

Abstract: 1.2μm – laser pumped wide frequency tunable coherent terahertz (THz) light source is demonstrated. The operation principle is based on difference frequency generation (DFG) with an excitation of phonon – polariton in Gallium Selenide (GaSe) crystal. The pump and signal lasers used are 1.2μm Cr:Forsterite lasers. The tuning range of the THz wave frequency covers from 0.3THz to 4.8THz (type eoo phase matching) and 8.3THz to 10.2THz (type eoo phase matching) under collinear phase matching conditions. It is shown that the maximum conversion efficiency is up to ~10^-6, which is 3 orders in magnitude larger than that of Gallium Phosphide (GaP) crystal.