Water/Propanol Solvent Makes 'Green' Lasers

The volatility, flammability and other environmental hazards posed by solvents used in dye lasers, such as methanol and ethanol, have hindered the lasers' use in industrial applications. The refractive properties and benign nature of water would make it an ideal replacement, but the organic dyes used in the lasers tend to mysteriously clump together in a water solvent.

A 70 percent water/30 percent n-propanol solution may be the answer. As reported in the March 20 issue of Applied Optics, researchers at the Bhabha Atomic Research Centre in Mumbai, India, have found this mixture to yield laser efficiencies comparable to ethanol when used in high-repetition-rate laser amplifiers. The binary solvent also holds a better photothermal figure of merit and lower vapor pressure than ethanol.