Stimulated emission of light from doped molecular crystals at 4.2 °K

Investigations were made of the spectral and energy characteristics of stimulated emission from doped molecular crystals at 4.2 °K. The molecular crystals used were naphthalene, biphenyl, dibenzyl, and fluorene, doped with derivatives of diarylethylenes and diaryldivinylbenzenes, naphthacene, azulene, anthracene, and others. The crystals were excited in the impurity absorption band by the third harmonic of a neodymium laser. The stimulated emission from the doped crystals at 4.2 °K was characterized by a narow line (0.5–5 cm^–1) and a stable emission frequency, which did not depend on the excitation energy or the impurity concentration. The stimulated emission from most of the crystals could be tuned continuously in a narrow frequency range by varying the sample temperature. The threshold pump energy density, the coefficient of conversion of the pump energy into stimulated emission energy, and the volume density of the stimulated radiation were determined. The prospects for using molecular crystals at 4.2 °K in laser engineering are discussed.