Silicon Fabry-Perot interferometer as an optical FIR component: Application to variable couplers with uniform transmission of FIR optically-pumped lasers

Abstract

The far-infrared characteristics of the double silicon etalon Fabry-Perot (FP) reflector are investigated. Measurements are reported at short FIR wavelengths. The low IR and FIR absorption and the high optimum reflectivity of this device allow convenient optimization of the coupling conditions of CW optically-pumped FIR lasers. Three sets of Si F. P. reflectors when chosen to cover complementary regions of the spectrum are adequate to cover between them most of the FIR range Using such a coupler respective output powers of 70 mW and 85 mW are obtained with the 70 μm and 118 μm CH3OH lasers operating on the EH11 mode for ≃16 W pump power injected in the FIR cavity. The variable reflector is also used to determine the unsaturated laser gain.