7 research outputs found
Optimisation of a compact cold-atoms interferometer for gravimetry
The work presented in this thesis focusses on the development of a transportable atom-interferometry experiment and a compact fibre laser system towards precision measurements of gravitational acceleration. Interference fringes are shown with clouds of cold 87Rb atoms using co-propagating laser beams to drive stimulated Raman transitions. This is demonstrated both inside and outside of laboratory environments for which an integrated and transportable experiment is constructed. Further improvements are presented that enable the generation of clouds containing 1.7 · 108 atoms at a rate of 2.5 Hz and having a temperature of (7 ± 1) µK. This is largely due to the development of a compact laser system based on all-fibre coupled components. It is demonstrated that the laser system designed here can achieve fast frequency sweeps over 1.8 GHz within 2 ms, making it widely applicable in compact atom-interferometry experiments with rubidium atoms. This is shown by creating a Mach–Zehnder type interferometer with counter-propagating Raman beams, thus enabling measurements of gravitational acceleration. Since the laser system uses only two lasers and one fibre amplifier, a significant reduction in size is achieved, as well as a decrease in the total power consumption of the overall experiment by a third to (162 ± 7) W
Spectroradiometer calibration for radiance transfer measurements
Optical remote sensing and Earth observation instruments rely on precise radiometric calibrations which are generally provided by the broadband emission from large-aperture integrating spheres. The link between the integrating sphere radiance and an SI-traceable radiance standard is made by spectroradiometer measurements. In this talk, the calibration efforts of a Spectra Vista Corporation (SVC) HR-1024i spectroradiometer are shown and how these enable radiance transfer measurements at the Calibration Home Base (CHB) for imaging spectrometers at the Remote Sensing Technology Institute (IMF) of the German Aerospace Center (DLR). Using this calibrated spectroradiometer, radiance transfer measurements are performed with relative expanded uncertainties between 1% and 3% (k = 2) over the wavelength range from 380 nm to 2500 nm, which are limited by the uncertainties of the applied radiance standard
Spectroradiometer Calibration for Radiance Transfer Measurements
Optical remote sensing and Earth observation instruments rely on precise radiometric calibrations which are generally provided by the broadband emission from large-aperture integrating spheres. The link between the integrating sphere radiance and an SI-traceable radiance standard is made by spectroradiometer measurements. In this work, the calibration efforts of a Spectra Vista Corporation (SVC) HR-1024i spectroradiometer are presented to study how these enable radiance transfer measurements at the Calibration Home Base (CHB) for imaging spectrometers at the Remote Sensing Technology Institute (IMF) of the German Aerospace Center (DLR). The spectral and radiometric response calibrations of an SVC HR-1024i spectroradiometer are reported, as well as the measurements of non-linearity and its sensitivity to temperature changes and polarized light. This achieves radiance transfer measurements with the calibrated spectroradiometer with relative expanded uncertainties between 1% and 3% (k=2) over the wavelength range of 380 nm to 2500 nm, which are limited by the uncertainties of the applied radiance standard
Application of optical single-sideband laser in Raman atom interferometry
A frequency doubled I/Q modulator based optical single-sideband (OSSB) laser
system is demonstrated for atomic physics research, specifically for atom
interferometry where the presence of additional sidebands causes parasitic
transitions. The performance of the OSSB technique and the spectrum after
second harmonic generation are measured and analyzed. The additional sidebands
are removed with better than 20 dB suppression, and the influence of parasitic
transitions upon stimulated Raman transitions at varying spatial positions is
shown to be removed beneath experimental noise. This technique will facilitate
the development of compact atom interferometry based sensors with improved
accuracy and reduced complexity
Performance of an optical single-sideband laser system for atom interferometry
This paper reports on a detailed performance characterization of a recently
developed optical single-sideband (OSSB) laser system based on an IQ modulator
and second-harmonic generation for rubidium atom interferometry experiments.
The measured performance is used to evaluate the noise contributions of this
OSSB laser system when it is applied to drive stimulated Raman transitions in
Rb for precision measurements of gravitational acceleration. The laser
system suppresses unwanted sideband components, but additional phase shift
compensation needs to be applied when performing frequency chirps with such an
OSSB laser system. The total phase noise contribution of the OSSB laser system
in the current experiment is 72 mrad for a single atom-interferometry sequence
with interrogation times of ms, which corresponds to a relative
precision of 32 n per shot. The dominant noise sources are found in the
relative intensity fluctuations between sideband and carrier components and the
phase noise of the microwave source.Comment: 16 pages, 8 figure