Operating ultracold quantum gas experiments outside of a laboratory environment has so far been a challenging goal, largely due to the lack of sufficiently stable optical systems. In order to increase the thermal stability of free-space laser systems, the application of nonstandard materials such as glass ceramics is required. Here, we report on Zerodur-based optical systems which include single-mode fiber couplers consisting of multiple components jointed by light-curing adhesives. The thermal stability is thoroughly investigated, revealing excellent fiber-coupling efficiencies between 0.85 and 0.92 in the temperature range from 17°C to 36°C. In conjunction with successfully performed vibration tests, these findings qualify our highly compact systems for atom interferometry experiments aboard a sounding rocket as well as various other quantum information and sensing applications.
Operating ultracold quantum gas experiments outside of a laboratory environment has so far been a challenging goal, largely due to the lack of sufficiently stable optical systems. In order to increase the thermal stability of free-space laser systems, the application of nonstandard materials such as glass ceramics is required. Here, we report on Zerodur-based optical systems which include single-mode fiber couplers consisting of multiple components jointed by light-curing adhesives. The thermal stability is thoroughly investigated, revealing excellent fiber-coupling efficiencies between 0.85 and 0.92 in the temperature range from 17°C to 36°C. In conjunction with successfully performed vibration tests, these findings qualify our highly compact systems for atom interferometry experiments aboard a sounding rocket as well as various other quantum information and sensing applications.
A number of cold atom experiments are restrained by the impeding effects of gravity.While efforts have been made to overcome these limitations in a gravitational environment, another approach is placing the experiment in a microgravity environment, as can be found aboard sounding rockets, satellites or a space station.The cornerstone of such experiments is a robust laser system.The adverse conditions during a rocket launch impose stringent requirements on thermal stability and resilience against mechanical stress on this part of the experimental setup.Furthermore, the very limited space found on any of the aforementioned microgravity platforms necessitates maximal miniaturization.In order to meet these requirements, we have developed a technology based on miniaturized free-space optics, mounted onto optical benches made from Zerodur, a glass-ceramic which exhibits a vanishing first order coefficient of thermal expansion.The technology has already been successfully implemented in the sounding rocket missions FOKUS, KALEXUS and MAIUS-1.It will also be used in the upcoming MAIUS-2/3 sounding rocket missions.To meet the even more restrictive size and mass constraints of the NASA-DLR Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL) mission, a quantum optics multi-user facility aboard the International Space Station, we are currently investigating a new and improved design concept.While being motivated by these missions, our technology can be expanded to any other experimental field where a small and robust laser system is needed.
Quantum-optical experiments situated in a gravitationally bound experimental setup are fundamentally limited in numerous ways, such as the gravitational sag experienced by the trapped atoms or the limited free-evolution times of an atomic interferometer.These constraints can be overcome by deploying the experiment in a microgravity platform, such as the International Space Station (ISS).The Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL), a collaboration between NASA and DLR and successor to NASA's CAL mission, aims to achieve just that.Planned as a multi-user experimental facility, it will enable numerous quantum-optical experiments with ultracold atomic clouds of different isotopes of rubidium and potassium in the microgravity environment of the ISS.The optical capabilities of this experiment will be manifold: Atoms can be cooled and trapped using a 2D-and 3D-magneto optical trap (MOT).They can then be loaded into a red-detuned crossed optical dipole trap.Using blue-detuned light, arbitrary painted optical potentials can be applied.Atom interferometry along two separate interferometry axes is also possible.Fluorescence and absorption detection are available for imaging of the atomic ensemble.In this paper, we present a compact and robust optical distribution system which is required to enable this functionality.To this end, we use a combination of fiber-to-fiber coupled optical benches, and fiber-based components.This distribution system needs to withstand the vibrational loads during launch to the ISS, and needs to retain a good fiber-to-fiber coupling efficiency under varying environmental conditions, such as temperature fluctuations, without maintenance, through the multi-year mission time.We have designed a total of ten optical benches, eight for light distribution and two as spectroscopic units.The optical benches make use of our micro-optical bench toolkit based on the glass-ceramic Zerodur, which has mechanical properties akin to aluminium and a negligible coefficient of thermal expansion.The toolkit has been
Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described. First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10-10mbar l/s at a base pressure of 10-11 mbar, exceeding the common ASTM E595 test.
Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described. First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10-10mbar l/s at a base pressure of 10-11 mbar, exceeding the common ASTM E595 test.
Ultra-cold quantum gases in space promise to boost the sensitivity of matter-wave interferometers. Applications of the latter extend from fundamental physics over the use in navigation to interdisciplinary applications such as geodesy, e.g. satellite gravimetry [1, 2]. Exploiting quantum gases for high-precision interferometry places high demands on their control and manipulation. We take benefit of various microgravity platforms such as the Bremen drop tower [3], the Einstein elevator in Hannover [4], sounding rockets [5,6] and the international space station [7] to advance the necessary methods. The DLR-mission MAIUS-1 demonstrated Bose-Einstein condensation and performed first interferometry experiments [4]. NASA’s Cold Atom Laboratory continues this research in orbit on the ISS [7]. In addition, atom interferometry is pursued in highly dynamic environments such as parabolic flights [8]. Starting from a rubidium Bose-Einstein condensate, recently lowest expansion energies have been achieved by us in the Bremen drop tower as required for extending atom interferometry over several seconds [9]. Extending these methods to quantum mixtures not only opens up new physics in the absence of buoyancy, but also faces challenges regarding their use for interferometry. Interferometers based on two chemical elements have been proposed for quantum tests of the equivalence principle on the ISS as well as on satellites. Currently we prepare a sounding rocket mission to investigate the simultaneous generation and manipulation of potassium and rubidium condensates [10]. Together with CAL [7], these experiments will prepare the DLR-NASA multi-user facility BECCAL for research on quantum gas mixtures and interferometry [11] as well as enhance the readiness level of methods required for STE-QUEST [12], a proposal for a satellite mission currently studied in an modified version within ESA’s VOYAGE 2050 program [13].
In this talk, I will review recent theoretical and experimental developments aimed at utilizing ultracold quantum gases for a wide variety of cavity QED applications. Ultrastable "clock" atoms when employed as an active medium in a laser-like system could potentially form the basis for producing coherent light of extreme frequency stability. The fundamental coherence limits with realistic experimental parameters appear to be competitive with the most ultrastable lasers developed to date. Furthermore, the coupling of high-Q atoms with spin-like analogues by optical resonators have interesting applications in both quantum metrology and sensing, and in quantum information science.