Tampere University of Technology

TUTCRIS Research Portal

Active optical clock based on four-level quantum system

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Pages (from-to)2033-2038
Number of pages6
JournalChinese Science Bulletin
Issue number17
Publication statusPublished - Jun 2013
Publication typeA1 Journal article-refereed


Active optical clock, a new conception of atomic clock, has been proposed recently. In this work, 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. 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.

ASJC Scopus subject areas


  • active optical clock, light shift, narrow linewidth, population inversion