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Finite-Difference Time-Domain Analysis of Wavelength-Selective Characteristics in Weighted Acoustooptic Switches for Wavelength-Division-Multiplexed Photonic Routing

Waveguide-type acoustooptic (AO) switches can switch optical waves wavelength-selectively for wavelength-division-multiplexed (WDM) signals. The switches can be expected to be used in WDM photonic networks. In this paper, finite-difference time-domain (FDTD) analysis is presented for wavelength-selective switching with a collinear weighted AO device consisting of an optical directional coupler, input/output Y-branches and a tapered surface acoustic wave (SAW) waveguide. The FDTD simulated results are compared with the result from the coupled mode theory. It is shown that a sidelobe level as low as -20 dB in the filtering characteristics is realized by using weighted AO interaction. It is also shown that the sidelobe structure is affected by the characterisitcs of the input Y-branch.