ETD

• frequency metrology
• laser frequency stabilization
• optical lattice clock

The subject of this thesis is the development of an atomic physics apparatus to study the possibility of a strontium (Sr) optical lattice clock at the European Laboratory for Nonlinear Spectroscopy (LENS), sited at the University of Florence.

Optical lattice clocks are predicted to surpass the present microwave atomic clock performaces both in terms of accuracy and frequency stability. The conceptual scheme of a Sr-based optical lattice clock is the following: cold Sr atoms trapped in an optical lattice are interrogated by a pre-stabilized laser beam (the “local oscillator”) on the 1S0 – 3P0 very narrow atomic transition (linewidth < 1 Hz). The laser frequency is then actively kept on the center of the absorption resonance by a feedback control loop, acquiring the stability of the atomic transition. The laser frequency so stabilized is sent to a femtosecond frequency comb. Frequency comb is employed to measure the absolute frequency of the laser radiation by counting the
beating of the local oscillator with one of the comb’s teeth.

The work of this thesis then consisted of two different experimental studies. Since frequency stabilization of the laser used as clock local oscillator is the first requirement to build an optical clock, we first realized a high purity laser probe by means of a commercial diode laser source. The second part consisted on the experimental demonstration of a high-resolution magnetically induced spectroscopy (MIS) of the 88Sr isotope clock transition for an atomic sample trapped in an optical lattice. The observation of a very narrow optical transition (less than 100 Hz) is the main result of this work.