THIN-FILM LASING FROM A DYE-DOPED SILICA TITANIA COMPOSITE/

Thin-film gain media with rhodamine-doped silica(SiO2)/titania(TiO2) c omposite films were fabricated by the sol-gel technique. Laser action was observed from the optically pumped films by controlling the thickn ess and refractive indices of the SiO2/TiO2 matrices. The existence of a thickness cutoff for gain narrowing and light trapping in an optica lly richer film with a higher TiO2/SiO2 ratio suggested the contributi on of multiple inward reflections of emitted Light within simple asymm etric planar waveguides. Moreover, the peak separation between the obs erved discrete waveguided modes was strongly indicative of lasing with a longitudinal resonant structure. (C) 1998 Elsevier Science B.V. All rights reserved.