Dark line resonances in Cs-Ne vapor microcells for chip scale atomic clocks

We report the characterization of Coherent Population Trapping (CPT) resonances in Cs vapor microcells filled with Neon (Ne) buffer gas. The impact on the atomic hyperfine resonance of some external parameters such as laser intensity and cell temperature is studied. We show the suppression of the first-order light shift by proper choice of the microwave power. The temperature dependence of the Cs ground state hyperfine resonance frequency is shown to be canceled in the 77-80°C range for various Ne buffer gas pressures. We preliminary demonstrate a 852 nm VCSEL-modulated based CPT atomic clock exhibiting a short term fractional frequency instability σ_y(τ) = 1.5×10^-10 τ^-1/2 until 200 s.