Tunable thin-film laser

An investigation was made of the spectral characteristics of a tunable thin-film laser with a distributed feedback. A short-wavelength shift of the frequency tuning range was discovered and studied as a function of the film thickness. The spectral composition of the emitted radiation was determined and it was demonstrated that the H and E waves could be excited separately. It was found that the refractive index of an activated film could be determined from the effective value of this index and from Δλ = λ_H – λ_E.