A TUNABLE LIGHT-SOURCE IN THE 370 NM RANGE BASED ON AN OPTICALLY STABILIZED, FREQUENCY-DOUBLED SEMICONDUCTOR-LASER

A tunable harmonic output power of 18 muW at a wavelength of lambda = 370 nm is obtained by resonance-enhanced frequency doubling of an optically-stabilized semi-conductor laser. A commercially available AlGaAs laser diode which emits a maximum power of 10 mW at lambda = 740 nm is operated in an extended-cavity configuration. Dispersion prisms are used in the extended cavity to obtain longitudinal-mode selection with low loss of optical power. The output is focussed into an optically isolated high-finesse ring resonator which contains a LiIO3 Crystal for second-harmonic generation. One potential application of this laser source is the optical excitation and laser cooling of ytterbium in an ion trap. In a related demonstration experiment, the frequency-doubled diode laser is applied to excite the lambda = 369.5 nm S-2(1/2)-P-2(1/2) transition of ytterbium ions in a hollow-cathode discharge.