PhD abstract
This thesis reports the development and characterization of an optical frequency reference at 895 nm based on the interrogation of cesium atoms confined in a microfabricated cell using dual-frequency sub-Doppler spectroscopy. This frequency reference includes a diode laser tuned on the cesium D1 line (895 nm), an electro-optic modulator, an acousto-optic modulator, a cesium vapor microcell and a control electronics.
Two nearly-identical laser systems were developed, one using a DFB diode laser and the other with an external cavity diode laser (ECDL). The beatnote between these two lasers demonstrated a frequency stability of 1.1×10-12 at 1 s, limited by the intermodulation effect induced by the laser frequency noise.
An ultra-stable frequency reference at 895 nm was developed to unambiguously characterize the individual performance of the microcell ECDL. The latter is based on an annex ECDL, phase locked to a spectrally-broadened frequency comb, referenced to an ultra-stable Fabry-Perot cavitystabilized 1542 nm laser. A compensated fiber link, with a residual phase noise of –55 dB‧rad²/Hz at 1 Hz, was developed to transfer the signal of the reference.
Beating with the reference, the microcell ECDL laser has demonstrated a short-term frequency stability of 2.9×10-13 at 1 s, in good agreement with its phase noise (+40 dB‧rad²/Hz at f = 1 Hz), and better than 5×10-14 at 100 s. These performances are competitive with the best current microcell frequency references.
In a last step, preliminary studies were initiated to measure the sensitivity of laser frequency to variations of some experimental parameters. Among the evaluated effects, the misalignment between both counter-propagating beams, the microwave power, and the magnetic field appear to be important contributions to the laser mediumterm stability.
Key words
frequency reference, cesium microcell, sub-Doppler spectroscopy, frequency stability, laser
PhD Thesis
Full document (FR) : HAL-04412404