Luminescence properties of Rh6G in silica xerogels

Abstract

Dye lasers are widely used, since they can be operated in pulsed or continuous manner and cover a large spectral range from the ultraviolet to the near infrared (using different dyes). However, laser dyes are usually used in liquid form thereby imposing restrictions on the laser design such as the need for a pumping system, reservoirs, etc. Hence the search for solid-state dye lasers with competitive lifetimes and efficiencies constitutes an active research field. The main approach is to embed the laser dye into a suitable matrix. The basic requirements imposed on the solid matrix are high optical quality with a low level of scattering and a wide range of transparency covering both pump and lasing wavelength. In addition a high damage threshold to laser radiation and good thermal and photochemical stability are required. Xerogels and aerogels have been used for this purpose for several years now and much progress has been achieved (see e.g. [1,2]). We have prepared silica xerogels by a standard procedure using tetra-ethylorthosilicate, ethanole, and hyrdochloric acid. The laser dye (Rhodamine6G) was dissolved in ethanole and added to the solution at various concentrations. After gelation the gels were dried in air for 2 days at 50C. The luminescence properties of the such prepared solid state dye hybrids were investigated by steady state and time resolved spectroscopy and compared to those of a solution of Rhodamine6G in methanole. We observe a slight blue shift in the luminescence maximum from about 590 nm in methanol to about 570 nm in the hybrids. The luminescence lifetime of Rhodamine6G after pulsed excitation with 470 nm wavelength is about 5.8 ns, both in the methanol solution and in the prepared dye hybrids. [1] M. Canva et al., Appl. Opt. 34, 428 (1995). [2] B. Sanchez et al., Adv. Mat. 15, 1969 (2003).