Frequency locking to a high-finesse Fabry-Perot cavity of a Frequency   doubled Nd:YAG laser used as the optical phase modulator
  We report on the frequency locking of a frequency doubled Nd:YAG laser to a 45 000 finesse, 87-cm-long, Fabry-Perot cavity using a modified form of the Pound-Drever-Hall technique. Necessary signals, such as light phase modulation and frequency correction feedback, are fed direcly to the infrared pump laser. This is sufficient to achieve a stable locking of the 532 nm visible beam to the cavity, also showing that the doubling process does not degrade laser performances. 
M. Bregant, G. Cantatore, F. Della Valle, G. Ruoso, G. Zavattini