To reduce the linewidth of Lamb dips, we introduce a cavity-enhanced absorption cell (CEAC) coupled with a Gaussian beam with a 1.9-mm 1/e2radius at the beam waist for the reduction of transit-time broadening. We state that transit-time broadening depends only on the beam radius at the beam waist. This fact is useful for the design of the CEAC, and a pair of concave and convex mirrors is thereby employed. We have carried out sub-Doppler resolution spectroscopy of the ν3band of CH4and the ν1band of CH3D using a difference-frequency-generation source and the CEAC, and the recorded Lamb dips narrow to 80 kHz (HWHM).
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics