Conversion efficiency of 56% in frequency doubling of single-frequency coherent light from Ti:sapphire laser at 778 nm in high-finesse resonant cavity containing BiBO crystal

Single-frequency coherent light from a Ti:sapphire laser at 778 nm was frequency-doubled efficiently in a high-finesse resonant cavity containing a BiBO crystal to generate an output at 389 nm, which was the resonant wavelength of 23S1 → 33P2 of 3He. The 389 nm cw coherent light was obtained with the conversion efficiency of 56%, even at the relatively low input power of about 700 mW. The laser frequency was also locked to the doubling-cavity resonance by the Hänsch–Couillaud technique.