Glasses embedded with IV-VI semiconductor quantum dots and their application for Q-switching of mid-infrared lasers

Summary form only given. We used the new P/sub 2/O/sub 5/-Na/sub 2/O-ZnO-AlF/sub 3/-Ga/sub 2/O/sub 3/ glass system for the formation of PbSe and PbS semiconductor quantum dots (SQD). Thermal treatment of initially colorless glasses at 390-440/spl deg/C led to their coloring to brown and black depending on the annealing. X-ray diffractometry of the annealed glass samples proved the existence of PbSe, PbS SQD with NaCl cubic structure in the glasses. Transmission electron microscopy of the samples demonstrated existence of spherical SQD with the size varied between /spl sim/2 and 15 nm depending on the duration and the temperature of the heat treatment. The measured spectrum of the secondary X-rays indicated the presence of lead and sulfur in the SQD. The optical absorption spectra of the annealed glass samples with PbS and PbSe SQD were measured in the spectral range 350-3500 nm at several temperatures. Sets of optical absorption peaks corresponded to different quantum transitions were clearly observed even in the spectra measured at room temperature, and the measurements at He temperature indicated narrow (/spl sim/5-7%) size distribution of the SQD. Theoretical analysis of the energy spectra and optical transitions was carried out in the framework of the four-band k/spl middot/p model with full account of the anisotropy effects. It was demonstrated that strong anisotropy of the energy bands of bulk PbSe, PbS resulted in the arising of additional optical transitions in the SQD. These anisotropy-induced optical transitions were clearly observed in the measured absorption spectra of the SQD. The calculated energy positions of the optical transitions coincided with the results of the measurements of optical absorption and luminescence spectra. Five optical transitions were distinguished and interpreted, and the calculated dependencies of the energies of these transitions versus the SQD size were in a good agreement with that obtained from the experimental data for 40-- 10 /spl Aring/ SQD diameter range.