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Strontium Optical Lattice clock

We report on our progress toward the realization of an optical frequency standard referenced to strontium intercombination lines. We have prepared the experimental setup for high resolution spectroscopy of the doubly-forbidden S0 P0 line on bosonic Sr atoms with magnetic field induced spectroscopy technique[1]. The transition have been observed with compact laser sources based on semiconductor devices. The clock laser is a 698 nm diode stabilized in two steps, with a cascaded lock to two resonant cavities with high finesse. The stabilization is used to reduce the emission linewidth of the laser down to Hz level. Reduced sensitivity of the cavity length to both thermal noise and acoustic noise is achieved by a specially cut of a 10 cm ULE spacer for symmetric horizontal suspension [2]. Our current setup allows the capture of more than 10 atoms of Sr in 1D optical lattice at the magic wavelength. The trapping laser is an infrared source at 813 nm based on a master ECDL delivering 50 mW that injects a tapered amplifier producing up to 600 mW optical power. Furthermore, a frequency comb based on a femtosecond Ti:Sapphire laser has been developed. This will be used for absolute frequency measurements of the clock light. The Ti:Sa laser has a repetition rate of 297 MHz, a pulse width of 50 fs and an output power of 500 mW (with a pump power of 4W). A photonic crystal fibre is used to generate a supercontinuum spectrum larger than one octave, and the offset frequency beat signal is obtained in a f-2f interferometer.