Rb-based stabilized laser system as frequency reference for CO2 monitoring

We present our ongoing development of a compact fiber-connectorized rubidium-based laser system as frequency reference for CO2 monitoring at 1572 nm. Part of the radiation of a continuous-wave master DFB laser emitting at 1560 nm is frequency-doubled to reach a rubidium absorption line at 780 nm for frequency locking. An optical frequency comb, generated from the other part of the master laser radiation injected into a resonant cavity that contains an electro-optical modulator, fills the 12-nm gap between the CO2 line and the master laser optical frequency. The frequency stability of the master laser and of one line of the frequency comb at 1557 nm was measured by heterodyning with a fully-stabilized Er-fiber optical frequency comb referenced to an H-maser. A fractional Allan deviation below or equal to 1×10-10 (20 kHz) was measured between 1 and 10 second integration time, improving down to below 1×10-11 (2 kHz) between 1'000 and 200'000 seconds.