The exploration of quantum physics has heralded a new era of quantum
sensors with improved measurement precision compared to conventional
systems. Quantum sensors based on alkaline-earth atoms
offer a particular high accuracy and improvement in comparison to
classic sensors. Laboratory based experiments are rapidly transitioning
to field applicable quantum sensors and have also seen a beginning
commercialization. To facilitate this transition, a reduction of
size, weight and power consumption in the form of miniaturization
of key components such as the magneto-optical trap is necessary.
In this work, I present design and characterization of two planar structures
for cooling on a broad-line and a narrow-line transition at two
different wavelengths with a single, incident bi-chromatic beam.
The first is a two-color grating magneto-optical trap (GMOT) optimized
for cooling and trapping of 88Sr atoms on the first and second
cooling transition. Secondly, a quasi-planar, achromatic Fresnel
structure for magneto-optical trapping combining the advantages of
achromaticity of the tetrahedral MOT with robustness, small size and
ample optical access of the GMOT is presented.
In the GMOT, 106 88Sr atoms are initially cooled on the 1S0 ! 1P1
transition at 461nm to few mK and subsequently transferred to the
second cooling stage on the narrow line 1S0 ! 3P1 transition at
689nm where they are further cooled to a temperature of < 5 K. A
transfer efficiency of 25% is reached. I outline general design considerations
for two-color cooling with a GMOT on a broad and narrow
transition transferable to other atom species.
In the so-called Fresnel MOT a comparable number of 88Sr were precooled
on the 1S0 ! 1P1 transition and subsequently cooled on the
1S0 ! 3P1 transition with a transfer efficiency of 50%. Here, they
were further cooled in the so-called broadband MOT to temperatures
of 20 K-40 K. Fermionic strontium was also successfully captured
in the first stage MOT. Due to its achromaticity, the Fresnel MOT can
be used for laser cooling of any atom where materials with suitable reflectivity
are available and can further be used for even multi-species
traps.
Furthermore, I analyze MOT dynamics in micro-gravity applications
regarding their temperature and number density and consequences
for trap design for space-borne applications.
These results enable compact, robust set-ups for multi-color MOTs
paving the way for largely miniaturized physics packages in quantum
sensing.
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