It is anticipated that ground-to-geostationary orbit (GEO) laser communication will benefit from pre-compensation of atmospheric turbulence for laser beam propagation through the atmosphere. Theoretical simulations and laboratory experiments have determined its feasibility; extensive free-space experimental validation has, however, yet to be fulfilled. Therefore, we designed and implemented an adaptive optical (AO)-box which pre-compensates an outgoing laser beam (uplink) using the measurements of an incoming beam (downlink). The setup was designed to approximate the baseline scenario over a horizontal test range of 0.5 km and consisted of a ground terminal with the AO-box and a simplified approximation of a satellite terminal. Our results confirmed that we could focus the uplink beam on the satellite terminal using AO under a point-ahead angle of 28 μrad. Furthermore, we demonstrated a considerable increase in the intensity received at the satellite. These results are further testimony to AO pre-compensation being a viable technique to enhance Earth-to-GEO optical communication.
Secure communication networks are the critical infrastructure of the information age. To ensure secure communication between governmental institutions and other high-security environments, the German Federal Ministry of Education and Research (BMBF) initiated an ambitious project -the QuNET initiative. In a joint effort, the Max Planck Institute for the Science of Light (MPL), the German Aerospace Center (DLR) and the Fraunhofer Society aim to develop the technological basis of a German quantum key distribution (QKD) infrastructure. This paper describes the infrastructure used in a first link demonstrator within this project and how we achieved the transition from initial quantum transceiver concepts to first link experiments.
The extreme adaptive optics deformable mirror as outlined in the study of EPICS for the EELT helps to detect planets much fainter than the observed star. In doing so, excellent wavefront quality ensured by a high actuator count is mandatory. A long actuator lifetime is equally important since it reduces the number of dead actuators to a minimum, which is necessary for the coronagraphy techniques.The Fraunhofer Institute of Applied Optics in Jena and Physik Instumente GmbH teamed up to response to an ESO Call for Tender. We developed an appropriate deformable mirror (DM) concept, and are currently elaborating the breadboards to demonstrate critical technologies. The considered DM technology is based on piezoelectric stack actuators which deform a thin-shell glass substrate. As a main feature, we provide a modular solution, meaning that actuator modules may be inserted into a DM substrate. With that an exchange of actuator modules in case of actuator failure is possible that characterizes the SWAP DM for extreme adaptive optics. In order to enable a high lifetime of the DM, we will pre-stress the actuator and use a modified PICMA® actuator, which exhibits a ceramic insulation extending the lifetime. Thus, the array benefits from an improved actuator lifetime without the requirement for an additional encapsulation which would be disadvantageous for the necessity of a low actuator pitch.In this project several laboratory breadboards will be developed to demonstrate key aspects of the deformable mirrors and their TRL level. We present the current state of the preliminary design, the schematic design and the status of the breadboards.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.