The Padé approximation with Baker’s algorithm is compared with the least-squares Prony method and the generalized pencil-of-functions (GPOF) method for calculating mode frequencies and mode Q factors for coupled optical microdisks by FDTD technique. Comparisons of intensity spectra and the corresponding mode frequencies and Q factors show that the Padé approximation can yield more stable results than the Prony and the GPOF methods, especially the intensity spectrum. The results of the Prony method and the GPOF method are greatly influenced by the selected number of resonant modes, which need to be optimized during the data processing, in addition to the length of the time response signal. Furthermore, the Padé approximation is applied to calculate light delay for embedded microring resonators from complex transmission spectra obtained by the Padé approximation from a FDTD output. The Prony and the GPOF methods cannot be applied to calculate the transmission spectra, because the transmission signal obtained by the FDTD simulation cannot be expressed as a sum of damped complex exponentials.
© 2009 Optical Society of America
Integrated Optics Devices
Original Manuscript: July 28, 2009
Revised Manuscript: September 24, 2009
Manuscript Accepted: September 25, 2009
Published: October 22, 2009
Yong-Zhen Huang and Yue-De Yang, "Calculation of light delay for coupled microrings by FDTD technique and Padé approximation," J. Opt. Soc. Am. A 26, 2419-2426 (2009)