Cascade pumping
The idea exploited by Balembois and colleagues involves pumping a Nd:GdVO4 crystal at 808 nm, which produces light at 912 nm, and then using this 912 nm emission to pump the 1064 nm transition in an Nd:YVO4 crystal, a process known as cascade pumping. The 1064 nm cavity is completely enclosed in the 912 nm cavity. In the final step, intracavity sum-frequency mixing at 912 and 1064 nm via a BiBO crystal produces light in the blue part of the spectrum. (Credit: François Balembois)