Use of stimulated scattering by polaritons in detection of submillimeter radiation

An experimental investigation was made of a detector of submillimeter radiation utilizing a difference frequency generated as a result of stimulated scattering by polaritons in a crystal of lithium niobate. When the pump pulse duration was 2τp = 18 nsec and the cross-sectional area of the pump beam was Qp = 0.17 cm2, about 4×105 photons with frequencies in the range 25–35cm−1 were detected in a solid angle Ω = 10 msr for the signal/noise ratio of 5. The experimental results were in qualitative agreement with theoretical estimates obtained allowing for the finite apertures of the interacting waves.