Frequency locking a dye laser to the central optical Ramsey fringe in a Ca atomic beam and wavelength measurement

The frequency of a dye laser is stabilized to the 3P1–1S0 intercombination line of 40Ca through use of the first-derivative signal of the Ramsey fringes detected in a Ca atomic beam. The long-term stability of the frequency of the Ca-stabilized dye laser is estimated to be a few kilohertz from the servo error signal. The wavelength of the Ca-stabilized dye-laser beam is measured by comparison with that for an I2-stabilized He–Ne laser, which is one of the current wavelength standards. The measured wavelength is evaluated to be 657.4594396 nm with an uncertainty of better than 1 × 10−9.