Subwavelength silicon microcavities.

We present a study of the first silicon microdisk resonators which are smaller than the free-space resonant wavelength in all spatial dimensions. Spectral details of whispering gallery modes with azimuthal mode number m = 4-7 are measured in microdisks with diameters between 1.35 and 1.89microm and are studied at wavelengths from 1.52 to 1.62microm. For the structures considered here, m = 5 is the highest azimuthal mode order in a subwavelength cavity and has measured Q = 1250. These results agree well with theoretical calculations using a finite difference frequency domain method and fit an exponential scaling law relating Q to disk radius via m.