Development of diode and fiber laser sources for a Sr+trapped-ion optical frequency standard

Abstract

The development of an all-solid-state systems of lasers is described for the cooling and probing of strontium ions in a radio-frequency (rf) trap. The Sr+ ions created within the rf trap are laser cooled by repeated cycling on the 422 nm 2S1/2 - 2P1/2 resonance transition. The 422 nm light was generated from a single mode 70 mW 844 nm diode laser, whose output was frequency doubled to 422 nm in a KNbO3 crystal inside a resonant enhancement cavity. Decays from the Sr+ upper resonance level into the 2D3/2 metastable state remove ions from the cooling cycle. This loss was prevented by driving the 1092 nm 2D3/2 - 2P1/2 transition using a Nd3+-doped fiber laser, diode-pumped at 826 nm. The 2S1/2 - 2D5/2 optical 'clock' transition at 674 nm has a natural linewidth of 0.4 Hz and may be probed with an AlGaInP laser diode. The laser diodes at 844 nm and 674 nm are both collimated using a piezo-mounted GRIN rod which also provides longitudinal mode selection. The spectral output is optically narrowed using resonant optical feedback.