Laser system for Doppler cooling of ytterbium ion in an optical frequency standard

A laser system for Doppler cooling of ytterbium ion on the transition in a single-ion optical frequency standard is developed. The second harmonic of a semiconductor laser with a wavelength of is used for cooling. The laser frequency is doubled in a nonlinear BiBO crystal embedded in a ring resonator, which also serves as a reference for laser frequency stabilisation. Second-harmonic power of is generated at a wavelength of . Diode laser radiation is modulated by an electro-optic modulator at to generate a sideband exciting the hyperfine component of the cooling transition that is not excited by resonant cooling light. The sideband relative intensity of a few percent proved to be sufficient to reduce the ion dwelling time in the state to less than and increase the cooling efficiency.