Absolute Te_2 reference for barium ion at 4554 nm

Precision atomic spectroscopy is presently the workhorse in quantum information technology, metrology, trace analysis, and even for fundamental tests in physics. Stable lasers are an inherent part of precision spectroscopy, which, in turn, requires absolute wavelength markers suitably placed corresponding to the atomic species being probed. Here, we present new lines of tellurium (Te2), which allows locking of an external cavity diode laser (ECDL) for precision spectroscopy of singly charged barium ions. In addition, we have developed an ECDL with an over 100 GHz mode-hop-free tuning range using a commercially available diode from Nichia. These two developments allow nearly drift-free operation of a barium-ion trap setup with one single reference cell, thereby reducing the complexity of the experiment.