Investigations for a Miniature Optical Frequency Reference Based on High-Contrast Sub-Doppler Resonance in a MEMS Cesium Vapor Cell

Many of modern quantum technologies require the development of high-performance and low-power consumption miniaturized devices such as laser systems, atomic clocks, magnetometers and other quantum sensors. These instruments are to date often based on the use of chip-size diode lasers and microfabricated (MEMS) cells filled with alkali atoms [1]. An interesting challenge concerns the development of miniaturized optical frequency references (OFR). Different approaches have been engaged in this direction. One of the most successful example is a rubidium microcell-based OFR, involving the two-photon spectroscopy technique. This approach has recently demonstrated a remarkable frequency stability level of 4.4×10–12 at 1 s [2]. The present study is focused on a simple alternative approach based on sub-Doppler spectroscopy (SDS) with counter-propagating light beams. We propose to use dual-frequency light beams with orthogonal linear polarizations and frequency difference w1–w2 = Dhfs, with Dhfs the frequency of the atom ground-state hyper-fine splitting. First dual-frequency sub-Doppler spectroscopy (DF SDS) experiments have been performed with cmscale cells [3,4]. In the present study, we present preliminary spectroscopy and frequency stability results of a laser stabilized using DF SDS with a Cs vapor microfabricated cell [5] (Fig.1a). An extended-cavity diode laser (ECDL) source and a Mach-Zehnder intensity EOM are used to obtain the dual-frequency light field. A forward beam goes through the cell and is then reflected by a mirror to create the backward beam.