We report on the studies of kinetics of broad-band generation via optical rectification into terahertz domain using a sample of LiNbO<sub>3</sub> partially filling a hollow metallic waveguide to increase the coherence length, enabling the observation of transition between phase-mismatched and phase-matched mechanisms of terahertz frequency generation.
Millimeter wave passive radiometric imager based on frequency scanning antenna is suggested. As a frequency scanning antenna, the periodically perturbed dielectric image waveguide is considered. In frequency range 30÷38 GHz, the scan of the main lob over 40° has been realized. Parallel multibeam forming is realized by means of the set of narrow bandwidth resonant modulators, each of them controlled by the own modulating frequency.
We present theoretical and experimental results of surface-emitted THz-wave difference frequency generation (DFG) in 2 dimensional (D) periodically poled lithium niobate (PPLN) crystal. The two orthogonal periodic structures compensate the phase mismatch in two mutually perpendicular directions of the optical and THz-wave propagation. The tunable 1.5 - 1.8 THz wave generation with impulse power of 0.1 mW and repetition rate 1 MHz is obtained. The opportunity of the power enhancement using an interference of THz fields generated by the both forward and backward propagating optical waves is investigated. The power and radiation pattern of generated of THz-wave are calculated in far-field approximation. Analysis of THz-wave DFG in 2D PPLN and its correlation with experimental data is presented.
The potentiality to increase light pulse conversion efficiency into pulses of the millimeter and submillimeter (GHz - THz) range using the waveguide partially filled with a nonlinear crystal is suggested. This technique has been theoretically substantiated and experimentally studied. Phase matching is defined by the degree of partial filling. The calculated data as well as the experimental results of the difference frequency generation in LiNbO<SUB>3</SUB>, ZnTe, GaAs and DAST crystals are presented. DAST refractive index as well as its tn(delta) have been measured in the 70 - 900 GHz frequency range.