Dispersion tailoring of a crystalline whispering gallery mode microcavity for optical Kerr frequency comb generation

The generation of an optical Kerr comb in whispering gallery mode (WGM) microcavities has been investigated for applications in frequency metrology, precise spectroscopy, and signal processing. Optical Kerr combs are generated via parametric frequency conversion, thus a high quality factor (Q) is essential for lowering the threshold power, and this can be achieved with crystalline microcavities in, for example, calcium fluoride (CaF
₂
) because of the low absorption coefficient of this material. An optical Kerr comb with a wide span is needed to obtain frequency stabilization with the f-2f self-referencing method, which requires an anomalous dispersion [1]. We used a computer controlled precise cutting machine to fabricate a dispersion controlled CaF
₂
microcavity with an anomalous dispersion to obtain exactly the same dispersion as we obtained in the numerical simulation.