Low power pumped high efficiency frequency doubling at 397.5 nm in a ring cavity

We report low pump power high-efficiency frequency doubling of a fundamental laser beam at 795 nm, corresponding to the rubidium D1 line, to generate UV light at 397.5 nm using a periodically poled KTiOPO4 (PPKTP) crystal in a ring cavity. We obtain maximum stable output power of 49 mW for mode-matc