|Nanoparticle-Polymer Laser Media
In the 1990s material scientists working on new solid-state dye laser gain media introduced hybrid polymer-silica dye-doped matrices in an effort to improve the thermal characteristics of polymer-based gain media. These matrices belong in the broader organic-inorganic category. A significant problem associated with these new dye laser matrices was the observed laser beam inhomogeneity (also known as "laser beam break-up"). Later it was determined that this phenomenon was the result of internal interference resulting from the interaction of coherent light and the polymer-silica structure present in the gain matrix (Duarte and Pope (1995)). In other words, the presence of silica was visible via the observed laser beam inhomogeneities.
A solution to this problem was demonstrated by Duarte and James in (2003) by the use of silica nanoparticle distributions in the polymer matrix. Thus, using advances in polymer gain media, and nanoparticle techniques, it was possible to satisfy the interferometric requirements necessary to achieve invisibility of nanoparticle distributions in the visible spectrum. This has been demonstrated experimentally in solid-state organic-inorganic dye-doped gain media and characterized via the detection of laser beam profiles.
The photograph shown here corresponds to Fig. 2 of Duarte and James (2003) and shows a near-Gaussian laser beam following propagation in a dye-doped nanoparticle-polymer composite gain medium. Further, laser oscillation was achieved in this medium which yielded a homogeneous near-Gaussian emission beam. The homogeneity of the laser beam provides elegant evidence that the silica nanoparticles (present in 30% weight by weight in the polymer matrix) are highly transparent and essentially invisible to the laser radiation. The use of nano-particles configured in core-shell structures, to enhance invisibility in laser media, is discussed in Duarte and James (2005). Further details are
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Published on the 13th of January, 2007; updated on the 27th of March, 2013.