Wavelength-scale microdisks as optical gyroscopes: A finite-difference time-domain simulation study

We have developed a finite-difference time-domain algorithm to simulate a wavelength-scale optical gyroscope based on a circular microdisk. In addition to the frequency shift, the rotation-induced changes in the quality factor and far-field emission pattern of the whispering gallery modes are studied. Compared to the closed cavity of same size and shape, an open cavity displays a larger frequency splitting by rotation, due to an increase of the mode size. When the disk dimension is on the order of the optical wavelength, the relative change in quality factor by rotation is over an order of magnitude larger than that in resonant frequency, due to enhanced evanescent tunneling of light. These results point to multiple methods for rotation sensing, monitoring the lasing threshold and the output power or the far-field emission pattern of a rotating microdisk laser, which can be much more sensitive than the Sagnac effect in ultrasmall optical gyroscopes.