Compact ultrastable laser system for spectroscopy of ²S_1/2 → ²D_3/2 quadrupole transition in ¹⁷¹Yb⁺ ion

We report the results of studying a compact laser system designed for manipulating a quantum state of the optical qubit based on the ²S_1/2 → ²D_3/2 quadrupole transition in the ¹⁷¹Yb⁺ ion at a wavelength of 435.5 nm. An emission power of the laser system reaches 500 μW at λ = 435.5 nm and the relative frequency instability of at most 3 × 10⁻¹⁵ is achieved at averaging intervals from 0.5 to 50 s with a subtracted linear frequency drift. The compactness of the developed system makes it possible to employ it in transportable systems including optical clocks. (laser spectroscopy)