Study On The SOI-MMI Optical Waveguide Units And Optical Switches

Multimode interference waveguide units, based on the principle of self-imaging in multimode waveguides, are widely applied in the integrated optics for their excellent characteristics, such as compactness, wide bandwidth, large manufacturing tolerances and so on. In this thesis, a series of SOI-MMI optical waveguide components and optical switches are studied.The principle of the MMI optical couplers was described and the distributing of the optical field was analyzed. The principle of the general MMI optical coupler, the paired interference and the symmetric interference MMI optical coupler were explained, moreover, the corresponding positions of the input optical field were introduced. The structure and operation principle of the hyperbola MMI optical coupler were also given.The 2×2 paired and hyperbola optical couplers were designed and optimized. The performances of the couplers were simulated with BPM. The effects of the variation of the size and the normalized width of the multimode waveguide on the output uniformity and excess loss were analyzed.The 1×4 symmetric MMI optical couplers with different background refractive index were designed and optimized. The effect on the characteristics of the couplers with different refractive index difference between the core and the background of the waveguide was studies.The 1.3/1.55μm paired and tilted MMI demultiplexers were designed and optimized. The contrast and insertion loss versus the structure parameters of the unit were given.The operating principle of the MMI Mach-Zehnder optical switch was briefly described. 1 × 4 and 4×4 SOI-MMI Mach-Zehnder optical switch were designed. The driving conditions of the optical switch were calculated and the distributions of the corresponding optical field were displayed.The operating principle of the partial index modulation optical switch wasexplained and 3X3 SOI-MMI partial index modulation optical switch was designed. The multimode waveguide was optimized, moreover, the extinction and cross-talk of the switch versus the length of the index modulation regions were given. At last, the optimum structure parameters of the switch were obtained.