Doppler-Free Stimulated-Emission Spectroscopy and Secondary Frequency Standards Using an Optically Pumped Laser

A new Doppler-free stimulated-emission technique using an optically pumped laser with applications in spectroscopy and optical frequency standards is reported. An argon-laser-pumped cw ${\mathrm{I}}_2$ laser is used to demonstrate the technique as well as measure the complete hyperfine structure of the ${\mathrm{I}}_2$ $B{{\mathrm{O}}_{\mathrm{u}}}^{+}-X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}$ (43,83) $P\left(13\right)\mathrm{}$ line. Hyperfine coupling strengths obtained for the $X{{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{}}^{+}{v}^{\prime \prime }=83\mathrm{}$, $J^{\prime \prime }=13\mathrm{}$ level are $\mathrm{eQ}{q}^{\prime \prime }=-1550.1\mathrm{}\pm 0.5$ MHz and $C^{\prime \prime }=59\mathrm{}\pm 5$ kHz. In addition, the ${\mathrm{I}}_2$ laser has been actively stabilized to within 1 kHz of the observed line center of an ${\mathrm{I}}_2$ hyperfine component.