Thesis of C.Cherfan
Soutenance de thèse
Amphithéâtre Pierre Glorieux
Thesis of C.Cherfan - laboratory Phlam
Abstract :
This thesis presents the development of an experimental system based on telecom fiber
amplifier technology for the production of 41K Bose-Einstein condensates. The long-term
scientific goal of this experiment is to study the Kicked Rotor model in the presence
of tunable interactions. The choice of the 41K isotope was made for two main reasons.
First, it is the only bosonic isotope of potassium that has a positive scattering length
(which facilitates condensation), and it has accessible Feshbach resonances. Secondly,
the wavelengths of the cooling transitions (766.701 and 770.108 nm) can be generated
by frequency doubling from powerful fiber laser sources in the telecom domain. This
gives the possibility to realize robust, stable and cost effective laser systems for cooling
and trapping of potassium.
The originality of our laser cooling system is that we generate all the useful frequencies,
before the power amplification and frequency doubling steps. We have also developed
a frequency stabilization technique and demonstrated its applicability in the cold
atom domain, also based on telecom technology, using ro-vibrational transitions of the
acetylene molecule. Finally, for the evaporative cooling, in an optical dipole trap, we
have built an original telecom laser system based on power control that does not require
any active element (electro- or acousto-optic modulators) in free space.
In parallel with the development of the telecom laser sources, we also developed the
rest of the experimental system (ultra-high vacuum system, magnetic traps, electronic
systems, etc). This allowed us to implement all the necessary steps towards the Bose-
Einstein condensation. Thanks to our laser systems, we magneto-optically trap 3 x 10^(9) atoms. Then, we performed cloud compression and gray molasses stages, using the D1 line, to reach temperatures of 16 µK and phase space densities of ~ 10^(-6). Next, we loaded the atoms into a hybrid trap (magnetic + optical trap), and finally into a crossed optical trap. We observed a condensate of 200 000 atoms in this trap, which will allow us to perform later experiments on the Kicked Rotor model in the presence of controllable interactions. Keywords : Bose-Einstein condensate,Potassium,Telecom domain,Kicked Rotor,Interactions
amplifier technology for the production of 41K Bose-Einstein condensates. The long-term
scientific goal of this experiment is to study the Kicked Rotor model in the presence
of tunable interactions. The choice of the 41K isotope was made for two main reasons.
First, it is the only bosonic isotope of potassium that has a positive scattering length
(which facilitates condensation), and it has accessible Feshbach resonances. Secondly,
the wavelengths of the cooling transitions (766.701 and 770.108 nm) can be generated
by frequency doubling from powerful fiber laser sources in the telecom domain. This
gives the possibility to realize robust, stable and cost effective laser systems for cooling
and trapping of potassium.
The originality of our laser cooling system is that we generate all the useful frequencies,
before the power amplification and frequency doubling steps. We have also developed
a frequency stabilization technique and demonstrated its applicability in the cold
atom domain, also based on telecom technology, using ro-vibrational transitions of the
acetylene molecule. Finally, for the evaporative cooling, in an optical dipole trap, we
have built an original telecom laser system based on power control that does not require
any active element (electro- or acousto-optic modulators) in free space.
In parallel with the development of the telecom laser sources, we also developed the
rest of the experimental system (ultra-high vacuum system, magnetic traps, electronic
systems, etc). This allowed us to implement all the necessary steps towards the Bose-
Einstein condensation. Thanks to our laser systems, we magneto-optically trap 3 x 10^(9) atoms. Then, we performed cloud compression and gray molasses stages, using the D1 line, to reach temperatures of 16 µK and phase space densities of ~ 10^(-6). Next, we loaded the atoms into a hybrid trap (magnetic + optical trap), and finally into a crossed optical trap. We observed a condensate of 200 000 atoms in this trap, which will allow us to perform later experiments on the Kicked Rotor model in the presence of controllable interactions. Keywords : Bose-Einstein condensate,Potassium,Telecom domain,Kicked Rotor,Interactions
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