Frequency stabilization of a novel 1.5-mu m Er-Yb bulk laser to a K-39 sub-Doppler line at 770.1 nm

The second harmonic output at 770.1 nm of a novel and compact Er-Yb:glass l aser was frequency stabilized against the sub-Doppler linewidth of a crosso ver line in the K-39 4S(1/2)-4P(1/2) transition as obtained by saturation s pectroscopy, Efficient frequency doubling, with a conversion efficiency of similar to 220% W-1, and with second harmonic power in excess of 15 muW, wa s achieved in a waveguide made in a periodically poled lithium niobate crys tal. As measured through the analysis of the closed-loop error signal, a la ser frequency instability of similar to 200 Hz was obtained; the Allan stan dard deviation of the frequency samples was below 4 x 10(-12) fur integrati on times tau between 100 ms and 100 s, and reached a lowest floor level of 8 x 10(-13) for 20 s less than or equal to tau less than or equal to 100 s. The measured frequency noise spectral density was in good agreement with t he analysis performed in the time domain. Compared to previously published data for stabilized solid-state laser sources in this wavelength region, th ese results represent a significant improvement in the frequency stability.