Abstract
The Sr optical lattice clock (Sr-OLC) is expected to be the next frequency standards, and the transportability has been improved. The requirements of lattice laser of Sr-OLC are the wavelength of 813nm, the output power more than 1 W, the linewidth of narrower than 1 MHz with single longitudinal and transverse mode. A Ti:Sapphire laser is currently used as the lattice laser. However it has disadvantage of its lack of long-term stable operation. This becomes one of the largest problems for space Sr-OLC. Therefore, as a new lattice laser, we have developed a master oscillator fiber power amplifier (MOPA) at around 810 nm with Tm3+-doped ZBLAN fiber. Since the phonon energy of ZBLAN fibers are lower than silica fibers, the upper state lifetime of 810 nm emission level of Tm3+-doped ZBLAN fiber (1350 µs) is much longer than that of Tm3+-doped standard silica fiber (14.2 µs) [1]. In the previous conference, we reported the maximum output power of 1.68 W at 813 nm with our MOPA system. However our MOPA system had the problem of its low reliability due to the photodarkening and low slope efficiency. In order to improve the operation property, we applied the dual-wavelength pumping and the real-time photobleaching. The experimental set up is shown in Fig.1.
© 2019 IEEE
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