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Deformable mirror for laser wavefront control
Deformable mirror for laser wavefront control
Paris Observatory - SYRTE
Wavefront aberration compensation with a DM.
Laser wavefront aberrations are the major limitation in a cold atom gravimeter. The interest of using microelectromechanical systems (MEMS) is to have an active deformable mirror (DM) to control the laser wavefronts in atom interferometers.
I characterised the DM response and implemented it in a cold atom gravimeter. As proof of principle, I inserted an optical element that I characterised on the way of the interrogation laser beam. I measured its effect on the interferometric phase and compensated it by adapting the shape of the mirror.
The results were published in Phys. Rev. Applied 7, 034016 (2017).
Atom chip for ultra-cold atoms generation
Atom chip for ultra-cold atoms generation
Paris Observatory - SYRTE
Using atom chips allows to obtain ultra-cold atoms in a very fast way, by using RF (radio-frequency) evaporative cooling with a deep magnetic trap.
I designed and built the magnetic trap in two stages. The first stage is at the macroscopic scale with 1.5 mm copper wires. The second stage is at micorscopic scale with 300 to 800 μm gold wires on a chip.
To make the chip, I developed a process in my laboratory, by evaporating two gold layers of 600 nm each on a aluminum nitride (AlN) substrat which follows the wire pattern.
To know the magnetic field generated by all the wires and the external coils, I wrote a flexible programme to simulate the magnetic field in 3D.
Simulation of magnetic field on two different planes.
Atom chip, with a macroscopic structure made of copper wires and a microscopic structure made of gold evaporated.
Coated vacuum chamber
Coated vacuum chamber
University of Birmingham - School of Physics and Astronomy
Reduce the background scattered light in atom interferometer will allow to reduce one source of noise. We used a commercially PCO35® coating, which is ultra-high vacuum compatible, to reduce the surface reflectivity.
This configuration show a reduction in the background light in cold atom experiment.
The results were published in AIP Advances 10, 105125 (2020).
Coated chamber.
Doppler compensated cavity
Doppler compensated cavity
University of Birmingham - School of Physics and Astronomy
Our approach involves combining a magnified linear cavity with an intracavity Pockels cell to induce voltage-controlled birefringence. This allows the cavity mode frequencies to follow the Raman lasers as they track gravitationally induced Doppler shifts, removing the dominant limitation of current cavity enhanced systems. The result is a cavity that simultaneously realizes Doppler compensation, a 5.8 mm diameter beam waist, and an enhancement factor of > 5 with a finesse of 35. The tunable Gouy phase enables the suppression of higher-order spatial modes and the avoidance of regions of instability.
This work has significant implications for the field of quantum technology, where power constrained applications can benefit from the reduction of optical aberrations and power enhancement. The absolute performance requirements of fundamental science are also addressed, where extended interferometry times can be achieved with increased contrast.
The results were published in Opt. Express 30, 30001-30011 (2022).
Cavity with Pockels cell and linearly polarized Raman beam.
Circulating pulse cavity enhanced
Circulating pulse cavity enhanced
University of Birmingham - School of Physics and Astronomy
We developed a new approach for extreme momentum transfer atom interferometry, which has the potential to significantly advance the sensitivity of large-scale atom interferometers. Our approach uses circulating, spatially resolved pulses and intracavity frequency modulation to overcome the limitations of high optical power and wavefront flatness requirements. We demonstrated the feasibility to realize 20 kW circulating pulses in a 1 km interferometer, enabling a momentum separation of over 104ℏk on the 698 nm clock transition in 87Sr.
The results were published in Commun Phys 4, 257 (2021).
Circulating pulses inside the cavity
Polychromatic pulses
Polychromatic pulses
University of Birmingham - School of Physics and Astronomy
Comparison between the monochromatic and polychromatic dynamics.
Atom interferometry is a critical technology that involves the coherent manipulation of atoms with light pulses, and enhancing pulse efficiency is essential for improving fringe contrast and sensitivity, especially for large-momentum transfer interferometers that use multiple pulses.
We investigates the optimization of the frequency domain of pulses using tailored polychromatic light fields, which is capable of delivering high-efficiency and resilient atom-optic pulses even in the presence of inhomogeneous atomic clouds and laser beams. We shown that this approach can operate over long interrogation times despite spontaneous emission and achieve experimentally relevant pulse efficiencies for clouds up to 100 μK. This breakthrough overcomes some of the most challenging barriers for large-momentum transfer, which has the potential to reduce the complexity of atom interferometers.
We demonstrated that polychromatic light pulses could enhance single-photon-based large-momentum transfer atom interferometry, achieving 850ℏk of momentum splitting with experimentally accessible parameters, representing a significant improvement over the current state-of-the-art. This work has far-reaching implications beyond atom interferometry and could enable groundbreaking advances in quantum state manipulation.
The results were published in EPJ Quantum Technol. 10, 9 (2023).
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