The Lasing Realization of Rb Four-Level Active Optical Clock

Since the concept of active optical clock has been proposed, the experimental research of Rb four-level active optical clock has never been carried out, but it has great value in research and application. First the Rb atoms are pumped from ground state 5S
_1/2
to 6P
_3/2
excited state by a narrow-linewidth 420 nm laser, and then decay to lower energy levels by spontaneous transitions, and immediately are pumped by pumping laser again. This process continues until the population inversion is established between 6 S and 5P states. Once the population inversion is built up, a Fabry-Perot type resonator, at a bad cavity regime whose cavity mode linewidth is much wider than that of the laser gain profile, is used to realize 1367 nm active optical clock laser output. As Rb atom 1367 nm 5P-6S excited state transition is in the communication E band, it can be used as a narrow-linewidth communication band optical frequency standard, which greatly improves the communication rate and accuracy.