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Frequency stabilization of an external-cavity diode laser with a thin Cs vapour cell

We demonstrate a novel method of stabilizing an external-cavity diode laser frequency to an atomic transition. This technique employs a sub-Doppler spectrum of Cs atoms in a thin 150 µm vapour cell. We obtain the result of the frequency fluctuation to be less than 0.8 MHz using the third derivative signal, with the root of Allan variance of the error signals reaching a minimum of 5.9 × 10−11 for an averaging time of 200 s.