Supercontinuum generation in macromolecular media

The interaction of intense, ultrashort (femtosecond) pulses of infrared light with water leads to the generation of a white light supercontinuum due to nonlinear optical effects. This supercontinuum extends over the wavelength range 400–900 nm. The blue-sided components of this supercontinuum are due to laser-induced plasma effects and are found to sensitively depend on the presence in water of minute quantities of protein dopants (dilutions of 0.025%–0.1%). Salivary proteins like mucin and immunoglobulin-A lead to pronounced suppression of the blue-sided components, while proteins found in blood serum, such as transferrin, immunoglobulin G (IgG) and human serum albumin (HSA), do not show any such suppression. It is postulated that major salivary proteins have a propensity to efficiently scavenge plasma electrons and thereby extinguish the plasma that is formed upon laser irradiation.