Abstract

A whispering gallery mode (WGM) microcavity made of crystalline material such as calcium fluorite (CaF₂) is very attractive because it has a very small material absorption coefficient [1], and makes it possible to obtain an ultra-high Q. A high Q cavity is of particular interest for frequency comb generation. It is known that dispersion management is another key to the efficient generation of such light. The cross-sectional shape of a waveguide is often altered to tailor the dispersion. However, the cross-section of a CaF₂ WGM microcavity is difficult to control because it usually requires mechanical polishing. Note that a conventional semiconductor process cannot be used to fabricate crystalline WGM microcavities.

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