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This is the profile of low beam-divergence near-single-transverse-mode emission from a tunable solid-state dye-doped polymer-nanoparticle laser (see Duarte and James (2003)). This class of emission has been demonstrated in the 563-610 nm range and also near 500 nm. The silica nanoparticles used in these experiments have an average diameter of 13 nm (present in 30% weight by weight in the polymer matrix) and are deployed in a fairly uniform distribution in the laser dye-doped polymer. Thus an organic-inorganic gain media is created with favorable dn/dT properties that yields uniform laser beams at ~ 1.3 times the diffraction limit. Note: the original images were recorded using silver-halide film media.
As explained in Duarte and James (2003; 2004) the homogeneity of the low divergence laser emission is due to the fact that the nanoparticles are distributed in the polymer in a sufficiently uniform manner so that they do not give rise to internal interference at visible wavelengths. Internal interference is the mechanism identified as responsible for beam break up in early forms (pre 2003) of dye-doped organic-inorganic nanocomposites.
F. J. Duarte and R. O. James, Dye-doped polymer nanoparticle gain medium, US Patent 6888862 (2005).
F. J. Duarte and R. O. James, Dye-doped polymer nanoparticle gain media for tunable solid-state lasers, in New Materials for Micropotonics (MRS, Warrendale, 2004) pp. 201-206.
F. J. Duarte and R. O. James, Spatial structure of dye-doped polymer-nanoparticle laser media, Appl. Opt. 43, 4088-4090 (2004).
F. J. Duarte and R. O. James, Tunable solid-state lasers incorporating dye-doped polymer-nanoparticle gain media, Opt. Lett. 28, 2088-2090 (2003).
W. Holzer, H. Gratz, T. Schmitt, A. Penzkofer, A. Costela, I. Garcia-Moreno, R. Sastre, and F. J. Duarte, Photo-physical characterization of rhodamine 6 G in a 2-hydroxyethyl methacrylate methyl methacrylate copolymer, Chem. Phys. 256, 125-136 (2000).
F. J. Duarte, A. Costela, I. Garcia-Moreno, R. Sastre, Measurements of dn/dT in solid-state dye-laser gain media, Appl. Opt. 39, 6522-6523 (2000).
F. J. Duarte and E. J. A. Pope, Optical inhomogeneities in sol-gel derived ORMOSILS and nanocomposites, Ceramic Transactions 55, 267-273 (1995).