PhD abstract
This PhD thesis presents the latest advances in SYRTE operational frequency chain, based on ultrastable oscillators at different wavelengths and frequency comb technologies. After describing this metrological architecture, the work focuses on the noise analysis of its critical elements so as to determine its stability and accuracy limits. The performance of these capabilities was measured by performing simultaneous comparisons of oscillators pairs with 3 fully independent chains. The relative resolutions obtained, below 1×10–16 in the microwave and 1×10–18 in the optical domains, demonstrate that these means of measurement are not a limiting factor, even with state-of-the-art clocks. A key element of optical clocks is the light probing the narrow atomic transition. While in practice ultrahigh stability lasers are built in the infrared range, the technique known as transfer of spectral purity makes use of a frequency comb to transmit its level of performance to target visible wavelengths (698 nm and 1 062 nm in the SYRTE case). This work demonstrates an out-of-loop transfer reaching a resolution better than 5×10–18 at 1 s. This lead to the first synchronized interrogation between the SYRTE strontium and mercury clocks when their respective clock lasers benefit from the transfer of a single master at 1 542 nm, resulting in a 2-fold improvement of their stability ratio measurement.
Key words
frequency chain, frequency metrology, optical clocks, optical frequency comb, spectral purity transfer, ultrastable laser