A Compact Optical Atomic Clock Based on a Two-Photon Transition in Rubidium

We present an optical rubidium atomic frequency standard (O-RAFS), based upon a two-photon transition at 778 nm, that utilized readily available commercial off-the-shelf components. Compared to existing GPS clocks, O-RAFS offers reduced short-term instability, improved manufacturability, and competitive size, weight, and power, making it an attractive candidate for future space operation.