Publications

Mid-infrared interference coatings with excess optical loss below 10 ppm

Author(s): Georg Winkler, Lukas W. Perner, Gar-Wing Truong, Ghang Zhao, Dominik Bachmann, Aline Mayer, Jakob Fellinger, David Follman, Paula Heu, Christoph Deutsch, Diane M. Bailey, Hartwin Peelaers, Stephan Puchegger, Adam J. Fleisher, Garret D. Cole, Oliver H. Heckl
Abstract: Low excess optical loss, combined absorption and scatter loss, is a key performance metric for any high-reflectance coating technology and is currently one of the main limiting factors for the application of optical resonators in the mid-infrared spectral region. Here we present high-reflectivity substrate-transferred single-crystal GaAs/AlGaAs interference coatings at a center wavelength of 4.54 µm with record-low excess optical loss below 10 parts per million. These high-performance mirrors are realized via a novel microfabrication process that differs significantly from the production of amorphous multilayers generated via physical vapor deposition processes. This new process enables reduced scatter loss due to the low surface and interfacial roughness, while low background doping in epitaxial growth ensures strongly reduced absorption. We report on a suite of optical measurements, including cavity ring-down, transmittance spectroscopy, and direct absorption tests to reveal the optical losses for a set of prototype mirrors. In the course of these measurements, we observe a unique polarization-orientation-dependent loss mechanism which we attribute to elastic anisotropy of these strained epitaxial multilayers. A future increase in layer count and a corresponding reduction of transmittance will enable optical resonators with a finesse in excess of 100,000 in the mid-infrared spectral region, allowing for advances in high-resolution spectroscopy, narrow-linewidth laser stabilization, and ultrasensitive measurements of various light–matter interactions.
Organisation(s): Faculty Center for Nano Structure Research
External organisation(s): National Institute of Standards and Technology, Gaithersburg, Thorlabs Inc., Crystalline Mirror Solutions GmbH, University of Kansas
Journal: Optica
Volume: 8
Pages: 686-696
No. of pages: 11
ISSN: 2334-2536
DOI: https://doi.org/10.1364/OPTICA.405938
Publication date: 05-2021
Peer reviewed: Yes
Austrian Fields of Science 2012: 103021 Optics
Keywords
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics
Portal url: https://ucrisportal.univie.ac.at/en/publications/78a5d8c5-d730-47b5-8e88-37e8e19ef1fe