光周波数標準器用超狭線幅ク口ックレーザーの開発

摘要

A diode laser is developed as an extremely narrow linewidth clock laser for a Ca~+ ion optical frequency standard. The required reduction of the linewidth was achieved by locking the laser to an ultrahigh-finesse ultralow expansion (ULE) glass reference cmvity. The long-term frequency drift is reduced by stabilizing the cavity temperature at the point where the coefficient of thermal expansion of the ULE material is zero. The laser linewidth is decreased down to 1-2 Hz. The frequency instability of the laser is 3 x 10~(15) at an averaging time of 1 s The long-term drift is only 0.03 Hz/s and it is compensated further. The Allan deviation is 3-4 x 10 5 over an averaging time of 50 s. The clock laser is distributed by an optical fiber of 40 m length for the observation of the ~2S_(1/2)-~2D_(5/2) transition of Ca~+ ions. The optical phase noise is canceled.