Precision frequency measurement of 1S0–3P1 intercombination lines of Sr isotopes*
Liu Huia),b), Gao Fenga), Wang Ye-Binga), Tian Xiaoa),b), Ren Jiea), Lu Ben-Quana),b), Xu Qin-Fanga), Xie Yu-Lina),b), Chang Honga)†
Fig. 1. Experimental setup for optical frequency measurement of the intercombination 5s 2 1 S 0 #cod#x2013;5s5p 3 P 1 transition of strontium. a Stabilized laser system at 689 nm. An ECDL is locked to a ULE optical cavity with a finesse of 12000 using the classical PDH method. b Atomic beam fluorescence spectroscopy system. The laser beam double-passes an AOM to detune the laser frequency. Simultaneously, the laser power is stabilized using the AOM. The atomic beam is collimated using a bundle of Monel-400 alloy capillaries and the detection region is magnetically shielded by three pairs of coils. The fluorescence collector and detector were specially designed. c Stabilized optical frequency synthesizer. The repetition rate and the offset frequency are locked to an active H-maser clock MHM 2010 #cod#x2122; . ECDL: external cavity diode laser. OI: optical isolator. ULE: ultra-low expansion cavity. QWP: quarter wave plate. PBS: polarizing beam splitter. EOM: electro-optic modulator. AOM: acousto-optic modulator. BB: beam block. PD: photo detector. SMF: single-mode fiber. VR: voltage reference. PI: Proportional integrating amplifier. VVA: voltage-variable attenuator. PA: power amplifier. EDFA: erbium-doped fiber amplifier. SHG: second harmonic generator. BDU: beat detector unit.