K Yu Khabarova

Ultrastable laser system for spectroscopy of the 1S0 – 3P0 clock transition in Sr atoms

A laser system with a spectral linewidth less than 1 Hz for spectroscopy of the 1S0–3P0 clock transition in strontium atoms has been demonstrated. A semiconductor laser emitting at a wavelength of 698 nm was stabilised to an external high-finesse Fabry–Perot cavity with vibration and temperature compensation near the zero expansion point. After laser cooling to a temperature below 3 μK, 88Sr atoms were loaded into an optical lattice at a magic wavelength of 813 nm. The laser system was used to characterise the 88Sr clock transition by magnetically induced spectroscopy. The resonance spectral width was determined to be 130 ± 17 Hz, which corresponds to a quality factor of 3 × 1012.

Secondary laser cooling of strontium-88 atoms

The secondary laser cooling of a cloud of strontium-88 atoms on the 1S0–3P1 (689 nm) intercombination transition captured into a magneto-optical trap has been demonstrated. We describe in detail the recapture of atoms from the primary trap operating on the strong 1S0–1P1 (461 nm) transition and determine the recapture coefficient κ, the number of atoms, and their temperature in the secondary trap as a function of experimental parameters. A temperature of 2 µK has been reached in the secondary trap at the recapture coefficient κ = 6%, which confirms the secondary cooling efficiency and is sufficient to perform metrological measurements of the 1S0–3P1 (698 nm) clock transition in an optical lattice.

Short-haul fibre-optic communication link with a phase noise compensation system for optical frequency signal transmission

A 5-m-long fibre link with a phase noise compensation system for optical frequency signal transmission at a wavelength of 1.14 μm is demonstrated. The stability of the noise compensation system in the presence of harmonic mechanical perturbations is assessed and the relative transmitted signal frequency instability is shown to be 3.8 × 10−15 at an averaging time of 1 s and 3.5 × 10−20 over 850 s.

Method of the production and trapping of thorium ions for nuclear transition investigation

This paper describes the techniques of production and trapping of thorium ions required to perform spectroscopic studies of thorium nuclear transition.

Spectroscopy of intercombination transition {sup 1}S{sub 0} – {sup 3}P{sub 1} for secondary cooling of strontium atoms

In the framework of the project aimed at creating an optical standard on cold Sr atoms we have realised sub-Doppler spectroscopy of the intercombination transition 1S0 – 3P1 (689 nm) in a cell with Sr vapour and in a cloud of atoms loaded in a magneto- optical trap (MOT). By measuring Zeeman splitting of the 3P1 level in the magnetic field of the MOT we have succeeded in fine adjustment of the MOT relative to a minimum of the magnetic field, which is necessary for successful secondary-stage cooling on the intercombination transition. In turn, absorption saturation spectroscopy in the vapour cell provides the long-term frequency stability of the second-stage cooling laser at λ = 689 nm.