Active optical clock based on four-level quantum system

• DOI: 10.1007/s11434-013-5877-0
• Publication Date: 2013-06-26T21:25:05Z
• Authors: TongGang Zhang; YanFei Wang; XiaoRun Zang; Wei Zhuang; JingBiao Chen
• Keywords: Quantum Physics; Atomic Physics (physics.atom-ph); FOS: Physical sciences; 7. Clean energy; 01 natural sciences; Physics - Atomic Physics; 0103 physical sciences; General; Quantum Physics (quant-ph); Physics - Optics; Optics (physics.optics)

5 pages<br/>Active optical clock, a new conception of atomic clock, has been proposed recently. In this report, we propose a scheme of active optical clock based on four-level quantum system. The final accuracy and stability of two-level quantum system are limited by second-order Doppler shift of thermal atomic beam. To three-level quantum system, they are mainly limited by light shift of pumping laser field. These limitations can be avoided effectively by applying the scheme proposed here. Rubidium atom four-level quantum system, as a typical example, is discussed in this paper. The population inversion between $6S_{1/2}$ and $5P_{3/2}$ states can be built up at a time scale of $10^{-6}$s. With the mechanism of active optical clock, in which the cavity mode linewidth is much wider than that of the laser gain profile, it can output a laser with quantum-limited linewidth narrower than 1 Hz in theory. An experimental configuration is designed to realize this active optical clock.<br/>