Tunable Terahertz Wave Research Articles

Terahertz wave amplification, stimulated by dc electric current, in grating coupled low-dimensional electron systems

We present an analytic theory of the transmission of electromagnetic waves through a structure “two-dimensional electron system with a flowing current – grating coupler.” The transmission coefficient T(ω,vdr) is calculated as a function of frequency, drift velocity vdr, and other physical and geometrical parameters of the structure. Threshold conditions for amplification [T(ω,vdr)>1] are analyzed. A number of ideas for a reduction of the threshold velocity and an enhancement of the amplification are proposed. Our results can be used for designing tunable solid-state terahertz wave amplifiers (generators), based on the grating coupled low-dimensional electron systems.

Characteristics of THz-wave radiation using a monolithic grating coupler on a LiNbO3 crystal

Wide tunable terahertz (THz) wave generation was successfully demonstrated utilizing a grating coupler fabricated on the surface of a LiNbO3 crystal which was pumped by a Q-switched Nd:YAG laser. In this paper, we report the detailed characteristics of the oscillation and the radiation including tunability, spatial and temporal coherency, directivity, and efficiency. Oscillation using a LiTaO3 crystal was also performed, in which experimental phasematching condition values agreed well with the calculated one.