Frequency stabilization of a frequency-doubled 197.2 THz distributed feedback diode laser on rubidium 5S1/2(right arrow)7S1/2 two-photon transitionsa

A 197.2 THz (1520.2 nm) ITU-T grid distributed feedback (DFB) diode laser is frequency stabilized at 197.198 THz by 1ocking its second harmonic (SH) signal on the rubidium 5S1/2(right arrow)7S1/2 twophoton transition at 394.396 THz (760.1 nm). With 100 mW from the DFB diode laser and amplifying by an erbium-doped fiber amplifier, we obtain an SH power of 15 mW using a periodically poled lithium niobate (PPLN) waveguide frequency doubler. The stability was 2× 10^-11 (10 s), corresponding to a frequency variation of 4 kHz at 1520.2 nm. Our scheme provides a compact and high performance frequency reference in the communication band.