Abstract
Recently we showed that the optical reflectivity of an interface formed by the elemental metal gallium and silica can become highly nonlinear when held at a temperature just below the bulk melting point of the metal.1 We have shown that such an interface can exhibit as much as 40% reversible change in reflectivity when excited with just a few mW of optical power. The phenomenon is extremely broadband (extending from at least 450 nm to 1700 nm), and is relatively fast (<1 ns rise time and < 1 µs recovery time). We believe that the effect is due to an optically-induced, surface-assisted phase transition of the confined α-gailium surface to some as yet unidentified metastable phase of a more metallic nature.2 We have already used the effect for a number of applications including the construction of broadband optical switches,3 and passive Q-switching of both erbium and ytterbium fiber lasers.4
© 2000 Optical Society of America
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