Two-stage stabilization setup of the laser working on 729 nm for spectroscopy with cold ⁴⁰Ca+ ion

The paper deals with the stabilization of an Extended Cavity Diode Laser (ECDL) working at 729 nm for precision spectroscopy with trapped and cooled ⁴⁰ Ca+ ion. For an interrogating and readout ion oscillation the laser with ultra-narrow linewidth is required. Main cornerstones are explained to achieve a laser with Hz or sub-Hz spectral linewidth. An optical setup for this laser and also the necessary electro-optic and electronic components are demonstrated. The paper presents the experimental design that comprises of the two-stage linewidth narrowing process and a facility for the frequency and noise analysis. The presented experimental results show the effect of the linewidth narrowing where the linewidth of the ECDL was narrowed down to a kHz level.