Two-photon, sub-Doppler hyperfine measurements of the $6\mbox{d} ^2\mbox{D}_j$ states of cesium

We measured the hyperfine structures of the $6\mbox{d} ^2\mbox{D}_j$ states of cesium using multiphoton, sub-Doppler absorption spectroscopy. In addition to improving upon the precision of previously published hyperfine coupling constants, we demonstrate a simplified approach to frequency calibration. Two narrow-band diode lasers excite cesium within a vapor cell in a two-step resonantly enhanced process. One laser is locked to the $6\mbox{s} ^2\mbox{S}_{1/2} (\mbox{F}) \rightarrow 6\mbox{p} ^2\mbox{P}_{3/2} (\mbox{F}')$ transition, and the second laser is scanned over the $6\mbox{p} ^2\mbox{P}_{3/2} (\mbox{F}') \rightarrow 6\mbox{d} ^2\mbox{D}_j (\mbox{F}'')$ hyperfine manifold. The frequency scale is directly referenced to the $^{87}$Rb ground state hyperfine transition, 5s$^2\mbox{S}_{1/2} (\mbox{F}=1) \leftrightarrow 5 \mbox{s} ^2\mbox{S}_{1/2} (\mbox{F}=2)$. We modulate the scanned laser frequency using an electro-optic modulator driven by an RF signal generator trained to a rubidium clock, and use the resulting sidebands for frequency calibration. The accuracy of this approach is demonstrated by measuring the hyperfine coupling constants of the $6\mbox{d} ^2\mbox{D}_{5/2}$ state, $\mbox{A} = -4.66 \pm 0.04 \,$MHz and $\mbox{B} = 0.9 \pm 0.6 \,$MHz, which agree with the literature\footnote{N. Georgiades, E. Polzik, and H. Kimble, Opt.\ Lett.\ {\bf 19}, 1474 (1994).}: $\mbox{A} = -4.69 \pm 0.04 \,$MHz and $\mbox{B} = 0.2 \pm 0.7 \,$MHz. We also improve upon the precision of previously reported $6\mbox{d} ^2\mbox{D}_{3/2}$ coupling constants\footnote{C. Tai, W. Happer, and R. Gupta, Phys.\ Rev.\ A {\bf 12}, 736 (1975).} ($\mbox{A} = 16.3 \pm 0.15 \,$MHz and $\mbox{B} < \pm 8 \,$MHz) by measuring $\mbox{A} = 16.34 \pm 0.05 \,$MHz and $\mbox{B} = -0.1 \pm 0.3 \,$MHz.