The solid host of a laser dye modifies its spectroscopic properties with respect to its liquid host. During the Sol-Gel process the dye molecules suffer from changing their environment. Two parameters affect this matter, the change in the concentration due to the evaporation of the solvent (drying) and the caging of dye molecules inside the pores or attachment to the silica network. Rhodamine 6G absorption and fluorescence spectra with different concentrations, during Sol-Gel time processing, have been studied. Both, absorption and fluorescence spectra of the dye in the solid host, for different concentrations, show a blue-shift relative to its liquid phase.
 A. Costela, I. García-Moreno, C. Gómez, O. García and R. Sastre: “Enhancement of laser properties of pyrromethene 567 dye incorporated into new organic-inorganic hybrid materials”, Chem. Phys. Lett., Vol. 369, (2003), pp. 656–661. http://dx.doi.org/10.1016/S0009-2614(03)00021-6
 T. Suratwala, Z. Gardlund, K. Davidson, D.R. Uhlmann J. Watson, S. Bonilla and N. Peyghambarian: “Silylated Coumarin Dyes in Sol-Gel Hosts”, Vol. 10, (1998), pp. 199–209.
 D. Avnir, D. Levy and R. Reisfeld: “The Nature of Silica Cage as Reflected by Spectral Changes and Enhanced Photostability of Trapped Rhodamine 6G”, J. Phys. Chem., Vol. 88, (1984), pp. 5956–5959. http://dx.doi.org/10.1021/j150668a042
 D. Avnir, V.R. Kaufman and R. Reisfeld: “Organic Fluorescent Dyes Trapped in Silica and Silica-Titania Thin Films by the Sol-Gel Method. Photophysical, Film and Cage Properties”, J. Non-Cryst. Solids, Vol. 74, (1985), pp. 395–406. http://dx.doi.org/10.1016/0022-3093(85)90081-X
 J. McKiernan, S. Yamanaka, B. Dunn and J. Zink: “Spectroscopy and laser action of rhodamine 6G doped aluminosilicate xerogels”, J. Phys. Chem., Vol. 94, (1990), pp. 5652–5654. http://dx.doi.org/10.1021/j100378a007
 M. Ahmad, T.A. King, D. Ko, B.H. Cha and J. Lee: “Performance and photostability of Xanthene and pyromettiens laser dye in different sol-gel phases”, J. Phys. D: Appl. Phys., Vol. 35(13), (2002), pp. 1473–1476. http://dx.doi.org/10.1088/0022-3727/35/13/303
 M. Ahmad, T.A. King, D.K. Ko, B.H. Cha and J. Lee: “Photostability of laser based on pyromethane 567 in liquid polymer, polymer host media”, Opt. Comm., Vol. 203(3–6), (2002), pp. 327–334. http://dx.doi.org/10.1016/S0030-4018(02)01179-3
 C.J. Brinker and G.W. Sherer: Sol-Gel Science, Academic Press, San Diego, 1990.
 T.M.H. Costa, H.S. Hoffmann, E.V. Benvenutti, V. Stefani and M.R. Gallas: “Pressure-induced changes on the optical properties and microstructure of silica-gel matrices doped with rhodamine 6G”, J. Opt. Mater., Vol. 27, (2005), pp. 1819–1824. http://dx.doi.org/10.1016/j.optmat.2004.11.006