ABSTRACT We propose a novel method of stabilizing laser oscillation frequency that uses a sub-Doppler spectrum of atoms in a thin vapor cell. An extended-cavity diode laser is frequency-locked to a hyperfine component of the Cs-D2 line. In the Allan-variance measurements on the beat note between two lasers thus stabilized, a frequency stability of 6.6 x 10-11 is achieved at an averaging time of 5.6 s. The frequency can be controlled even when the laser beam intensity is as small as 70 nW/cm2.
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