Optical fibers not much thicker than a human hair today not only constitute the backbone of our world-wide infor­mation exchange. They are also the basis for building extremely compact and robust sensors with very high sensi­tivity for tempera­ture, chemical analysis and much more. Optical resonators or filters are important com­ponents cutting out very narrow spectral lines from white light sources. In the simplest case such filters are built from two opposing mirrors tossing light back and forth as precisely as the pendulum of a clock work. The color of the filtered light is set by the mirror separation.

Suitable mirrors with high quality have been inte­grated with the end of such hairlike fibers for some time. Researchers of the University of Bonn have succeeded to build in a simple way such hairlike optical fiber reso­nators. They are not only extremely compact and stable but also allow to tune their color: they have glued the fiber ends carrying the mirrors into a common ferrule which can be stretched by means of a piezo crystal and hence control the mirror separa­tion. “The miniaturised optical filter makes a further contri­bution to making photonics and quantum techno­logies the decisive technology of the 21st century,” says Dieter Meschede from the Institute of Applied Physics at Uni­versity of Bonn. The scientist is a member of “Matter and light for quantum computing” (ML4Q) Cluster of Excellence of the Uni­versities of Bonn and Cologne and RWTH Aachen University.

Minia­turized highly stable optical precision filters are promising multiple appli­cations: they can store light energy within such a small volume such that already single photons can be efficiently stored and manipulated. Their high sensi­tivity suggests to build extremely compact and selective sensors, e.g. for detecting atmo­spheric gases. Using even more stable materials for the ferrule tiny optical clock works with extremely high frequency stability may be built.

In addition to the University of Bonn, the Univer­sidad de Guanajuato (Mexico) is also involved in the study. The project is funded within the FaResQ project of the program key components for quantum techno­logy of the Federal Ministry of Research and Technology (BMBF). The infra­structure for manu­facturing and processing the fibers takes place in the “Bonn Fiberlab”, which is operated by the ML4Q Cluster of Excellence. (Source: U. Bonn)

Reference: C. Saavedra et al.: Tunable fiber Fabry-Perot cavities with high passive stability, Opt. Exp. 29, 974 (2021); DOI: 10.1364/OE.412273

Link: ML4Q – Matter and Light for Quantum Computing, University of Bonn, Bonn, Germany