JOKARUS - Design of a compact optical iodine frequency reference for a sounding rocket mission

We present the design of a compact absolute optical frequency reference for space applications based on hyperfine transitions in molecular iodine with a targeted fractional frequency instability of better than $3\cdot 10^{-14}$. It is based on a micro-integrated extended cavity diode laser with integrated optical amplifier, fiber pigtailed second harmonic generation wave-guide modules, and a quasi-monolithic spectroscopy setup with operating electronics. The instrument described here is scheduled for launch end of 2017 aboard the TEXUS 54 sounding rocket as an important qualification step towards space application of iodine frequency references and related technologies. The payload will operate autonomously and its optical frequency will be compared to an optical frequency comb during its space flight

The Bose-Einstein Condensate and Cold Atom Laboratory

© 2020, The Author(s). Microgravity eases several constraints limiting experiments with ultracold and condensed atoms on ground. It enables extended times of flight without suspension and eliminates the gravitational sag for trapped atoms. These advantages motivated numerous initiatives to adapt and operate experimental setups on microgravity platforms. We describe the design of the payload, motivations for design choices, and capabilities of the Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL), a NASA-DLR collaboration. BECCAL builds on the heritage of previous devices operated in microgravity, features rubidium and potassium, multiple options for magnetic and optical trapping, different methods for coherent manipulation, and will offer new perspectives for experiments on quantum optics, atom optics, and atom interferometry in the unique microgravity environment on board the International Space Station

Technology roadmap for cold-atoms based quantum inertial sensor in space

Recent developments in quantum technology have resulted in a new generation of sensors for measuring inertial quantities, such as acceleration and rotation. These sensors can exhibit unprecedented sensitivity and accuracy when operated in space, where the free-fall interrogation time can be extended at will and where the environment noise is minimal. European laboratories have played a leading role in this field by developing concepts and tools to operate these quantum sensors in relevant environment, such as parabolic flights, free-fall towers, or sounding rockets. With the recent achievement of Bose-Einstein condensation on the International Space Station, the challenge is now to reach a technology readiness level sufficiently high at both component and system levels to provide "off the shelf"payload for future generations of space missions in geodesy or fundamental physics. In this roadmap, we provide an extensive review on the status of all common parts, needs, and subsystems for the application of atom-based interferometers in space, in order to push for the development of generic technology components

STE-QUEST - Test of the Universality of Free Fall Using Cold Atom Interferometry

In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources

Design of a dual species atom interferometer for space

Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth's gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species $^{85}$Rb/$^{87}$Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry, the detection unit, the vacuum system for $10^{-11}$ mbar ultra-high vacuum generation, and the high-suppression factor magnetic shielding as well as the thermal control system. The laser system is based on a hybrid approach using fiber-based telecom components and high-power laser diode technology and includes all laser sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and switching of the laser beams is carried out on an optical bench using Zerodur bonding technology. The instrument consists of 9 units with an overall mass of 221 kg, an average power consumption of 608 W (819 W peak), and a volume of 470 liters which would well fit on a satellite to be launched with a Soyuz rocket, as system studies have shown.Comment: 30 pages, 23 figures, accepted for publication in Experimental Astronom

Technology roadmap for cold-atoms based quantum inertial sensor in space

Recent developments in quantum technology have resulted in a new generation of sensors for measuring inertial quantities, such as acceleration and rotation. These sensors can exhibit unprecedented sensitivity and accuracy when operated in space, where the free-fall interrogation time can be extended at will and where the environment noise is minimal. European laboratories have played a leading role in this field by developing concepts and tools to operate these quantum sensors in relevant environment, such as parabolic flights, free-fall towers, or sounding rockets. With the recent achievement of Bose–Einstein condensation on the International Space Station, the challenge is now to reach a technology readiness level sufficiently high at both component and system levels to provide “off the shelf” payload for future generations of space missions in geodesy or fundamental physics. In this roadmap, we provide an extensive review on the status of all common parts, needs, and subsystems for the application of atom-based interferometers in space, in order to push for the development of generic technology components

The Bose-Einstein Condensate and Cold Atom Laboratory

Microgravity eases several constraints limiting experiments with ultracold andcondensed atoms on ground. It enables extended times of flight withoutsuspension and eliminates the gravitational sag for trapped atoms. Theseadvantages motivated numerous initiatives to adapt and operate experimentalsetups on microgravity platforms. We describe the design of the payload,motivations for design choices, and capabilities of the Bose-Einstein Condensateand Cold Atom Laboratory (BECCAL), a NASA-DLR collaboration. BECCALbuilds on the heritage of previous devices operated in microgravity, featuresrubidium and potassium, multiple options for magnetic and optical trapping,different methods for coherent manipulation, and will offer new perspectives forexperiments on quantum optics, atom optics, and atom interferometry in theunique microgravity environment on board the International Space Station

Verbesserung der Strahlqualität von Breitstreifendiodenlasern hoher Ausgangsleistung mit Hilfe eines externen Resonators

Das Verhalten von Hochleistungsbreitstreifenlasern in einem externen Resonator wird im Hinblick auf Verbesserungen der lateralen Strahlqualität untersucht. Dazu wird ein einfacher Messaufbau verwendet, der aus einer Breitstreifenlaserdiode als Gainmedium, zwei Linsen und einem externen Spiegel besteht. Das vorgestellte Konzept basiert darauf, dass die aktive Zone der Laserdiode als räumlicher Filter für höhere Resonatormoden dient. Geometrien des externen Resonators, welche für einen lateralen Grundmodebetrieb geeignet sind, werden aus einem theoretischen Modell abgeleitet, das auf dem ABCD-Matrix Verfahren für Gaussstrahlen beruht und die sich in Breitstreifenlasern ausbildende thermische Linse beinhaltet. Ein neuartiges experimentelles Verfahren, welches die thermische Linse einer Breitstreifenlaserdiode in einem externen Resonator quantifiziert, wird entwickelt. Der thermische Linsenkoeffizient wird, für verschiedene Injektionsströme und Pulsbreiten, bestimmt. Die Verlässlichkeit dieser Methode wird, durch den Vergleich der erhaltenen Ergebnisse mit den Werten von unabhängigen Messungen zur Ermittlung des thermischen Linsenkoeffizienten und durch die Simulation der Temperaturverteilung in der Laserdiode, verifiziert. Der Laser mit externem Resonator besteht aus der zu untersuchenden Breitstreifenlaserdiode mit einer Emissionswellenlänge von ungefähr 1.06 µm, zwei Linsen und einem Spiegel. Des Weiteren dient ein justierbarer Spalt innerhalb des Resonators als zusätzlicher Raumfilter. Die Abhängigkeit der Ausgangsleistung und der Strahlqualität von der Resonatorlänge und der Spaltbreite wird bei Injektionsströmen von 1 A und 5 A untersucht. Bei beiden Injektionsströmen verbessert sich die Strahlqualität deutlich, wenn die Länge des Resonators und die Breite des Spaltes auf die optimalen Werte eingestellt werden. Bei den Experimenten mit einem Injektionsstrom von 1 A entsprechen die optimalen Bedingungen den theoretischen Voraussagen. Bei 5 A Injektionsstrom müssen sie jedoch experimentell bestimmt werden, da das Verhalten des Lasers nicht mehr durch das Modell des passiven Resonators erklärt werden kann. Den Maßstab zur Beurteilung der Laserperformance stellt, im Gegensatz zu identischen freilaufenden Lasern, die maximale Ausgangsleistung gewichtet mit dem M² Wert dar. Unter diesem Gesichtspunkt wird, bei einen Injektionsstrom von 1 A und einer Ausgangsleistung von 0.35 W der M² Wert von 9.0 auf 3.5 verbessert. Bei einem Injektionsstrom von 5 A und einer Ausgangsleistung von 2.5 W wird der M² Wert von 18.7 auf 5.6 verbessert. Das zweite Resultat ist, mit den besten Ergebnissen von Breitstreifenlaserdioden in einem externen Resonator über die in der Literatur berichtet wird, vergleichbar.The operation of high-power broad area laser diodes in an external resonator is studied with respect to the improvement of their lateral beam quality. A simple setup with a broad area laser diode as gain medium, two lenses and an external mirror is considered. The concept relies on the ability of the active region of the laser diode to act as a spatial filter for higher order modes oscillating inside the resonator. The geometries of the external cavity laser that favor fundamental mode operation in the lateral direction are inferred with the help of a theoretical model based on the ABCD-matrix treatment of Gaussian beams in a passive stable resonator. Thermal lensing that arises in the broad area laser diode is included in the model. A novel experimental procedure that quantifies the thermal lens arising in the broad area laser diode to be used inside the external resonator is developed. The thermal lens coefficient is determined for different injection currents and pulse widths. The reliability of the method is validated by the comparison of the obtained results with values of the thermal lens coefficient derived from independent measurements. The external cavity laser comprising a test broad area laser diode that emits at a wavelength in the region of 1.06 µm, two lenses, and an external mirror is implemented. Additionally, an adjustable intra-cavity slit that serves as a supplementary spatial filter is inserted in the setup. The evolution of the output power and of the beam quality of the device as a function of the length of the resonator and of the width of the slit is studied at injection currents of 1 A and 5 A It is observed that at both injection currents, the beam quality of the emission is significantly improved when the length of the resonator and the width of the slit are adjusted to their optimal values. In the case of the experiments at an injection current of 1 A, the optimal conditions for the operation of the external resonator correspond to the theoretical predictions, but, at an injection current of 5 A, they have to be determined experimentally since the behavior of the laser cannot be explained by the model of the passive resonator anymore. The criterion used to assess the performance of the external cavity laser, as compared to a similar free running laser, is the maximum output power weighted by the M² value. In that respect, at an injection current of 1 A the M² value is improved from 9.0 to 3.5, with an output power of 0.35 W. At the injection current of 5 A the M² value is improved from 18.7 to 5.6, with a corresponding output power of 2.5 W. The latter result compares with the best values reported in the literature for the operation of broad area laser diodes in an external resonator

Durchstimmbarer-Mikrosystem-Diodenlaser - DuMiDiL : Abschlussbericht

[no abstract available