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.
A miniature endomicroscope is presented that combines a large field-of-view (up to 1.7 mm) for OCT-imaging and a high-resolution mode with 360 μm field-of-view (NA = 0.5) for multi-photon fluorescence or OCT imaging. The 4.7x magnification variation is achieved by the axial positioning of an inner micro-optical lens group using an integrated electro-magnetic z-actuator. A reverse fiber-optic piezotube-scanner with minimized length is employed for the image acquisition by resonant spiral scanning. With the probe diameter of 2.7 mm and a rigid length of about 60 mm, the approach may pave the way to clinical applications of these two modalities in a single probe.
Pre-compensation of atmospheric wavefront distortions using adaptive optics (AO) provides a promising approach for stabilizing optical feeder links in Earth-to-space laser communication applications.
The High-Power Focus Mirror we present in this paper gives access to dynamic focus position adaptation along 3.6 mm in high-power laser manufacturing. We developed and tested a new thermo-mechanical design for a unimorph deformable mirror that provides an extensive focal length range down to -2 m focal length. Moreover, the mirror’s unique thermal characteristics enable high-power applications up to 6.4 kW (2000 W/cm²) with stable optical beam quality as thermal lensing is successfully suppressed. Thus, the laser’s optical beam quality M² is stable over the entire actuation and thermal range.
We will describe the design and the characterization of the High-Power Focus Mirror. The mirror setup is based on a unimorph concept using a piezoelectric actuator and a thin glass substrate with a highly reflective multilayer coating. An integrated copper layer improves the heat dissipation. Providing maximum stroke, as well as excellent dynamic properties, the deformable mirror substrate is mounted by our established compliant cylinders [1].
Furthermore, we investigate the incorporation of the High-Power Focus Mirror into a commercial laser-cutting system. We set up a laser-cutting test bench including a multimode laser source, the focus mirror, a commercial laser processing head, and measuring instruments. In this assembly, we measure the achievable focus position range as well as the laser beam quality.
With this focus mirror, we want to encourage new, innovative high-power application fields in 3D laser processing such as laser cutting, welding, and structuring.
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