Sub-Doppler spectroscopy of molecular iodine at 531 nm using a frequency-doubled alpha-distributed feedback laser

We report, for the first time, the observation of the iodine hyperfine tran sitions at 531 nm using a frequency-doubled alpha-distributed feedback (alp ha-DFB) laser. The moderate high power of the alpha-DFB laser allows us to generate the second harmonic light by a periodically-poled LiNbO3 single-pa ss frequency doubler. We can stabilize this laser frequency to the hyperfin e component a(10) of R(94) 34-0 or R(70) 33-0 I-2 line, and the preliminary frequency stability was about 5 x 10(-11). This laser system is an attract ive frequency standard at 531 nm due to its compact size, high reliability, and low cost.