Dependences of the spectra of second harmonics generated in tellurium and proustite on the phase-matching band

A wide pumping spectrum was used in an experimental study of the spectra of second harmonics as a function of the length and dispersion properties of the nonlinear medium. The pumping source was a CO₂ laser in which Q switching was performed by a rotating mirror and a prism inside the resonator. The output wavelengths were 9.3, 9.6, 10.2, and 10.6 μ. The spectrum of the second harmonics generated in long (14 mm) tellurium crystals consisted of two or three lines separated by 0.02 μ; in short crystals the generated harmonics corresponded to a range of pumping wavelengths 0.3 μ wide. The harmonics of all four pumping wavelengths were generated simultaneously in proustite crystals. A strong focusing of the beam expanded the spectrum of the harmonics generated in tellurium until it overlapped the whole pumping spectrum.