Selective emission and luminescence of under intense laser excitation

Abstract

The microstructure of polycrystals synthesised by laser heating is studied. The synthesis of erbium silicate () layers was observed upon interaction of and melts. The dependences of the selective emission (SE) and luminescence spectra of polycrystals in the range on the intensity of laser-thermal (at the wavelength ) and resonant laser () excitation are investigated. The emission of heated polycrystals arises as a result of multiphonon relaxation of absorbed energy and is a superposition of the SE at the electronic-vibrational transitions of ions and the thermal radiation of the crystal lattice. The shape of the SE spectra of polycrystals in the range almost does not change upon laser-thermal heating from 300 to and subsequent cooling and corresponds to the absorption spectra of ions. With increasing temperature, the thermal radiation intensity increases faster than the SE intensity, and the shape of the spectrum becomes closer to the calculated spectrum of a blackbody. The anti-Stokes luminescence spectra of ions formed under intense laser excitation of the level are explained by additional SE caused by heating of the crystal matrix due to the Stokes losses. A difference between the SE and luminescence spectra is observed at low intensities of resonant laser excitation and low temperatures, when only the Stokes luminescence occurs. The temperature dependences of the SE and luminescence spectra of upon laser excitation testify to the fundamental role played by the interaction of the electronic -shell of ions with crystal lattice vibrations in the processes of multiphonon radiative and nonradiative relaxation. The laser-thermal synthesis is promising for inprocess variation of the chemical composition of rare-earth samples.