Caltech applied physicists create ultrahigh-Q microcavity on a silicon chip

In an advance that holds promise for integrating previously disparate functions on a chip, applied physicists at the California Institute of Technology have created a disk smaller than the diameter of a human hair that can store light energy at extremely high efficiency. The disk, called a “microtoroid” because of its doughnut shape, can be integrated into microchips for a number of potential applications. Reporting in the February 27, 2003, issue of the journal Nature, the Caltech team describes the optical resonator, which has a “Q factor,” or quality factor, more than 10,000 times better than any previous chip-based device of similar function. Q is a figure-of-merit used to characterize resonators, approximately the number of oscillations of light within the storage time of the device.