Population l 88Sr atomic beam for active optical clock

An active optical clock can provide laser light source with potential much narrower linewidth than that of conventional cavity stabilized laser for optical clocks since many cavity noises, including the Brownian thermal noise, can be reduced by orders of magnitude. In this report, a scheme of active optical clock based on Sr atomic beam is proposed. The experimental work of population inversion has been done. A 689 nm laser is used to realize the population inversion between (5s5p)³P₁ state and (5s²)¹S₀ state by the method of adiabatic rapid passage. A pumping rate of 59% is obtained. In order to establish the population inversion more effectively, an experimental scheme is proposed with a 483 nm pumping laser. A 687 nm laser is used for verification of pumping effectiveness. The atoms left in ground state after 689 nm laser and 687 nm laser pumping is about 7%, which may mainly result from ⁸⁷Sr isotope.