Cs microcell optical reference at 459 nm with short-term frequency stability below 2 × 10−13

Abstract

We describe the short-term frequency stability characterization of external-cavity diode lasers stabilized onto the 6S1/2−7P1/2 transition of Cs atoms at 459 nm, using a microfabricated vapor cell. The laser beatnote between two nearly identical systems, each using saturated absorption spectroscopy in a simple retroreflected configuration, exhibits an instability of 2.5 × 10−13 at 1 s, consistent with phase noise analysis, and 3 × 10−14 at 200 s. The primary contributors to the stability budget at 1 s are the FM-AM noise conversion and the intermodulation effect, both emerging from laser frequency noise. These results highlight the potential of microcell-based optical references to achieve stability performances comparable to that of an active hydrogen maser in a remarkably simple architecture.