A precise calibration system for high-resolution visible-laser spectroscopy

Publisher Website
Google Scholar
Abstract
A method for calibrating high‐resolution laser spectra in the visible is described. The system is based on an evacuated Fabry–Perot étalon whose cavity length is servolocked to a stabilized HeNe laser; the absolute order number of the fringe at the HeNe frequency is known and the free spectral range can be determined with high accuracy. For absolute‐frequency measurements the order number of a transmission fringe is obtained from a commercial wavemeter (whose accuracy is sufficient to identify the fringe); the absolute frequency is then the HeNe frequency multiplied by the ratio of the ‘‘unknown’’ order number to the ‘‘lock‐point’’ order number. The long‐term frequency reproducibility of the system is better than 25 MHz. Small‐frequency splittings such as molecular hyperfine intervals can be measured to ±1 MHz, while large‐frequency intervals (of the order of 500 GHz) are consistent to better than 10 MHz.