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Silicon microcavity arrays with open access and a finesse of half a million

Research output: Contribution to journalLetter

Georg Wachter, Stefan Kuhn, Stefan Minniberger, Cameron Salter, Peter Asenbaum, James Millen, Michael Schneider, Johannes Schalko, Ulrich Schmid, André Felgner, Dorothee Hüser, Markus Arndt, Michael Trupke

Original languageEnglish
Article number37
JournalLight: Science and Applications
Issue number1
Publication statusPublished - 10 Apr 2019

King's Authors


Optical resonators are essential for fundamental science, applications in sensing and metrology, particle cooling, and quantum information processing. Cavities can significantly enhance interactions between light and matter. For many applications they perform this task best if the mode confinement is tight and the photon lifetime is long. Free access to the mode center is important in the design to admit atoms, molecules, nanoparticles, or solids into the light field. Here, we demonstrate how to machine microcavity arrays of extremely high quality in pristine silicon. Etched to an almost perfect parabolic shape with a surface roughness on the level of 2 Å and coated to a finesse exceeding F = 500,000, these new devices can have lengths below 17 µm, confining the photons to 5 µm waists in a mode volume of 88λ 3 . Extending the cavity length to 150 µm, on the order of the radius of curvature, in a symmetric mirror configuration yields a waist smaller than 7 µm, with photon lifetimes exceeding 64 ns. Parallelized cleanroom fabrication delivers an entire microcavity array in a single process. Photolithographic precision furthermore yields alignment structures that result in mechanically robust, pre-aligned, symmetric microcavity arrays, representing a light-matter interface with unprecedented performance.

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