Compact 459-nm Cs Cell Optical Frequency Standard with 2.1×10−13/τ Short-Term Stability

Abstract

We achieve a compact optical frequency standard with an extended cavity diode laser locked to the 459-nm $6{S}_{1/2}$-$7{P}_{1/2}$ transition of thermal ${}^{133}\mathrm{Cs}$ atoms in a $\ensuremath{\phi}10\phantom{\rule{0.1em}{0ex}}\mathrm{mm}\ifmmode\times\else\texttimes\fi{}50\phantom{\rule{0.1em}{0ex}}\mathrm{mm}$ glass cell, using modulation transfer spectroscopy (MTS). The self-estimated frequency stability of this laser is $1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}/\sqrt{\ensuremath{\tau}}$. With heterodyne measurement, we verify the linewidth-narrowing effect of MTS locking and measure the frequency stability of the locked laser. The linewidth of each laser is reduced from the free-running 69.6 to 10.3 kHz after MTS stabilization, by a factor of 6.75. The Allan deviation measured via beat detection is $2.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}/\sqrt{\ensuremath{\tau}}$ for each MTS-stabilized laser. In addition, we measure the hyperfine structure of the $7{P}_{1/2}$ energy level based on the heterodyne measurements, and calculate the magnetic dipole constant A of the Cs $7{P}_{1/2}$ level to be 94.38(6) MHz, which agrees well with previous measurements. This compact optical frequency standard can also be used in other applications that require high-stability lasers, such as laser interferometry, laser cooling, geodesy, and so on.