Ultra high Q crystalline microcavities

Abstract

AbstractWe report on the fabrication technique of ultra high Q optical crystalline whispering gallery mode microresonators and discuss theirproperties. The technique is suitable for the majority of available optical crystals and for production of resonators with small size. Tovalidate the method, we made CaF 2 resonators with Q factors exceeding 4 · 10 8 and a diameter smaller than 100 lm. A single moderesonator has also been fabricated. Possible utilization of these new resonators in quantum optics is discussed. 2006 Elsevier B.V. All rights reserved. PACS: 42.50. p; 42.60.DaKeywords: Whispering gallery modes; Microcavity; Single mode resonator; Diamond turning; Cavity QED 1. IntroductionAlthough the whispering gallery mode resonators(WGMR) were invented almost a century ago, significantadvances in their actual utilization appeared only in the lastcouple of decades following the invention of efficient reso-nator-light coupling methods. The WGM resonances, alsoknown as morphology dependent resonances, have provento be useful in many photonics and optics applications.Miniaturization of these resonators makes new applica-tions possible in precision physics experiment [1,2].Historically, the WGM resonators have been fabricatedwith a variety of materials including silicon [3], sapphire,fused silica [4], calcium fluoride, lithium niobate [5] andother optical glasses and crystals. The optically transparentcrystals are particularly interesting for fabrication of theresonators because they naturally have many specific opti-cal [6] and spectroscopic features, such as zero phononlines, which are absent in amorphous materials. Anotheradvantage of crystalline materials for the fabrication ofthe resonators is that they can be stable against humidity,as in the case of CaF