Immersion Liquids for Ruby Lasers

A search was made for high index of refraction liquids suitable for immersion of ruby crystals in high-energy lasers. One liquid, SnCl2 · 2H2O in glycerin, is reported which can exactly match the index of ruby (1.76) and which, at the same time, is stable to the flash-lamp environment and transparent at the ruby pumping and lasing wavelengths. Another liquid, saturated aqueous SnCl2 · 2H2O, has a slightly lower index (1.60), but is more generally useful because of its low viscosity. Eight additional liquids with indices in the range from 1.43 to 1.54 are reported and tables are included which list the relevant properties of all of the liquids considered.