Abstract

Frequency-stabilized sources near 1550 nm are required as frequency references in dense wavelength-division-multiplexed fiber-optic communication systems, for precision measurement instruments and for fiber-optic sensing Locking to narrow sub-Doppler lines is required in order to obtain higher frequency stability and accuracy. A narrow and highly stable frequency reference that can be reached by frequency-doubling 1556 nm sources is the Rb two-photon transition near 778 nm^[1]. However, detection of this transition requires relatively high second harmonic power, typically in the mW range. In previous experiments that explored this transition, the second harmonic beam was only in the µW range, hence another pump laser was required at 778 nm. Owing to recent progress in optical amplifiers and in waveguide frequency doublers, we have now obtained sufficiently powerful second harmonic signal for direct detection and locking to the rubidium transition, using a single 1556 nm source

© 2000 IEEE