Acta Optica Sinica, Volume. 29, Issue 8, 2099(2009)
Coupling Characteristics of Spatial X-Crossing Waveguides
Spatial X-crossing waveguides consist of two vertically stacked waveguides crossed in an X type shape. These kinds of devices can be served as vertical couplers, vertical coupler filters, vertical optical switches and optical add/drop multiplexers. Based on the perturbation theory, a technique named equivalent field matching method (EFMM) is presented for analyzing the coupling characteristics of spatial X-crossing waveguides. The field profile of the rectangular waveguide is treated as a perturbation to radially symmetric fiber, and more accurate calculation of the coupling lengths of the spatial X-crossing waveguides is presented with the effect of corner regions taken into account. And the three-dimensional full-vector beam propagation method (3D-BPM) is used to verify these analytical results. Comparison of the coupling lengths obtained by the 3D-BPM and EFMM shows that the maximum relative error is 1.2%, and the average relative error is 0.9%. Results show that this proposed method is more convenient compared with other numerical methods. The equivalent field matching method is extremely useful in the accurate design of three-dimensional integrated optical devices based on spatial X-crossing waveguides.
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Sun Yiling, Jiang Xiaoqing, Yang Jianyi, Wang Minghua. Coupling Characteristics of Spatial X-Crossing Waveguides[J]. Acta Optica Sinica, 2009, 29(8): 2099