Quantum Optics laboratory of the Institute of Atomic Physics and Spectroscopy, lead by Prof. Janis Alnis, traditionally focused on precise measurements of light frequencies for optical frequency standards (optical clocks) probing atomic resonances with laser stabilised to a high-finesse optical resonator characterised by a femtosecond optical frequency comb up to 14 digits of precision. Also environmental monitoring of air pollutant gases with laser spectroscopy.