High-performance, compact optical standard

We describe a high-performance, compact optical frequency standard based on microfabricated Rb vapor cell and low-noise, external cavity diode laser operating the two-photon transition at 778 nm. The achieves an instability of 1.8x10$^{-13}$/$\sqrt{\tau}$ for times less than 100 s flicker noise floor 1x10$^{-14}$ out to 6000 s. At long integration times, is limited by variations in probe power AC Stark shift. retrace was measured 5.7x10$^{-13}$ after 30 hours dormancy. Such simple, yet high-performance could be suitable as accurate realization SI meter or, if coupled with comb, atomic clock comparable hydrogen maser.