17 Janvier – Thesis defense - Hodei Eneriz

14 h30 Amphi - Institut d'optique d'Aquitaine (Talence)

Atom–cavity interactions and grey molasses in a bow–tie resonator.

This thesis investigates interactions between cold atoms and laser light inside a bow–tie cavity. Ultracold rubidium 87 atoms are created at the center of the cross–shaped cavity arms at 1560 nm, where a far–off resonance dipole trap (FORT) is created.
Cooling of an atomic gas to ultracold temperatures requires a multistage process:  laser cooling in a magneto–optical trap (MOT); sub–Doppler cooling; loading into a conservative magnetic or optical trap; and often evaporative cooling.  Sub–Doppler cooling schemes involving dark states have emerged as a powerful technique: they are known as gray molasses.
In this context, we show that dark state cooling in an hyperfine two–photon Raman condition can be used in combination with FORT when strong differential light shifts are present. Additionally, we utilize this technique to cool the atomic ensemble in the FORT by further detuning the Raman beams to the red.
In another set of experiments,  we exploit the doubly resonant character of the cavity, both  at  1560  and  780  nm,  to  explore  the  interaction  between  the  atoms  and  the  cavity. Experimentally, continuous 780 nm laser light injection has been afforded by improvements on the 1560 nm frequency lock to the cavity, where ultracold atoms loaded into the FORT can collectively interact strongly with the 780 nm light.
By using similar two–photon techniques to the ones demonstrated in the gray molasses scenario, we introduce Raman pulses into the cavity and observe atom–induced cavity inter-arm photon exchange processes which we characterize by analyzing the produced momentum distributions on the ultracold atomic clouds.
References:
Loading and cooling in an optical trap via hyperfine dark states. D. S. Naik, H. Eneriz, M.
Carey, T Freegarde, F. Minardi, B. Battelier, P. Bouyer, and A. Bertoldi, Phys. Rev. Research 2, 013212 (2020).
All-Optical Bose-Einstein Condensates in Microgravity. G. Condon, M. Rabault, B. Barrett,
L. Chichet, R. Arguel, H. Eneriz, D. S. Naik, A. Bertoldi, B. Battelier, A. Landragin, and P.
Bouyer, Phys. Rev. Lett. 123, 240402 (2019).

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