Numerical analysis of the whispering gallery modes by the finite-difference time-domain method

The finite-difference time-domain (FDTD) method is used to analyze the whispering-gallery modes of microdisk lasers. The method takes no a priori assumption. It solves the Maxwell's equations directly while taking into account the actual structure of the microdisk. The numerical results are in agreement with experimentally measured spectrum. Our Q values, however, are higher than previously published theoretical results. By calculating the resonant wavelengths and Q factors for different disk sizes, we demonstrate that the FDTD can be used to optimize the design of microdisk lasers.