Laser system for secondary cooling of⁸⁷Sr atoms

Precision laser spectroscopy in fundamental studies

“…In 2006, we developed a temperature-and vibrationisolated resonator made from a special material Ð ultralow expansion (ULE) glass [38]. Attracting a set of novel approaches [27,39], we decreased the laser frequency instability to the level of thermal noise, which corresponds to a spectral line width of less than 1 Hz. A number of systems were developed at LPI for different wavelengths: 698 nm (clock transition in strontium), 689 nm (secondary cooling transition in strontium), 1140 nm (clock transition in thulium), and 531 nm (secondary cooling transition in thulium), and the quality factors of the resonators reached values of up to 3 Â 10 5 .…”

“…Typical relative instability of clock lasers (linear drift is not taken into account). Curve 1 represents the result of a comparison of two laser systems made at LPI with the standard stabilization system relative to ULE-resonators with a quality factor of 50,000 [39]. Curve 2 is the result of a comparison of two systems with additional feedback loops and a maximum ULE-resonator quality factor (300,000) [38].…”