arXiv:1805.06112 · Journal of the Optical Society of America B
Frequency stabilization of a 650 nm laser to an I2 spectrum for trapped Ba138+ ions
Tian Xie, Naijun Jin, Ye Wang, Junhua Zhang, Mark Um, Pengfei Wang, Kihwan Kim
Abstract
Optical manipulation of Ba+ ions is performed mainly by a 493 nm laser for the S1/2−P1/2 transition and a 650 nm laser for the P1/2−D3/2 transition. Because the branching ratio between the 493 and 650 nm transitions of a single Ba+ ion is comparable, stabilization systems of both lasers are equally important for Doppler cooling, sub-Doppler cooling, optical pumping, and state detection. The stabilization system of a 493 nm laser to an absolute Te2 reference has been well established. However, the stabilization of a 650 nm laser to the absolute reference of an atomic or molecular spectrum has not been presented before, to our knowledge. Here, we experimentally obtain the I2 spectrum near 650 nm and provide the experimental connection to the spectrum of Ba+. We present the 20 spectral lines of I2 in the range of 0.9 GHz above the resonance of the P1/2−D3/2 transition. We stabilize the 650 nm laser through the optical cavity to the lowest one among these lines, which is about 350 MHz apart, as the absolute frequency reference. Finally, we measure the frequency differences between these iodine lines and the Ba+ resonance through the fluorescence excitation spectrum with well-resolved dark states, which is in agreement with the theoretical expectation. The presented stabilization scheme enables us to perform precise experiments with Ba+ ions.