Research on stabilization of the frequency of a single longitude mode optical fiber laser

Abstract

An optical fiber laser that can continuously emit high stable single frequency laser is researched. The resonant cavity of the optical fiber laser is a compound ring resonator which is made with double sub ring resonant cavities sharing almost the same optical path. By employing erbium-doped fiber as the gain medium of the resonant cavity, the light of gain spectrum of the resonant cavity is obtained by using a fiber Bragg grating (FBG) to reflect the light of one of the fringes transmitting through a Fabry-Perot etalon (F-P1) which is inserted into the resonant cavity to filter the fluorescence emitted from the erbium-doped fiber pumped with a 980 nm laser. When the longitudinal mode spacing of the resonant cavity is adjusted to be corresponding to the linewidth of the gain spectrum, single frequency laser will oscillate. One of the transmitting frequencies of another Fabry-Perot etalon (F-P2) which is placed outside the resonant cavity is used as the basis of the laser’s frequency. Part of the fiber resonant cavity is wound on a PZT tube which is actuated by the output voltage of an electronic compensating circuit to adjust the resonant cavity length and thus the laser’s frequency will be stabilized at the transmitting frequency of F-P2 that is used as the basis. The stability of the frequency of the optical fiber laser can be higher than 10−8.