| Nowadays,on-chip optical interconnect technique has attracted considerable interest,which becomes a popular and promising technique for breaking the bottleneck of traditional electronic interconnects.In the construction of high performance optical interconnect systems on chip,silicon-based photonics integrated circuits(PICs)has advantages of high index-contrast and CMOS-compatible processing,which meets the development requirements of high-speed and large-capacity optical information processing system.Optical power divider and polarization beam splitter are fundamental and vital devices for silicon-based PICs.The former can be utilized in realization of multichannel optical power splitting,and the latter is used in realization of polarization beam splitting with high efficiency.In this thesis,two types of optical power dividers and a polarization beam splitter using subwavelength gratings(SWG)structure in SOI platform are proposed and analyzed in detail,where structure parameters are optimized and fabrication tolerances are presented,and the proposed devices can provide potential devices for building dense integration PICs.Firstly,the development of PICs is reviewed in brief,in which key issues,fabrications,development tendency and challenges are briefly described.Afterwards,current status of optical power dividers and polarization beam splitters are introduced in detail,and key performance parameters of on-chip silicon passive devices are also presented.Secondly,two commonly used numerical techniques for analyzing optical waveguides and devices are introduced,and SWG is analyzed in detail by these methods.The modal characteristics and transmission properties are analyzed by finite-difference frequency-domain(FDFD)method and finite-difference time-domain(FDTD)method,respectively.Noted that SWG can be employed to design and/or fabricate various kinds of photonic devices with high performance due to the advantages of index manipulation,diffraction suppression and reflection suppression.Next,a polarization-insensitive power divider using SWG is proposed and analyzed based on the above analysis of the SWG structure,in which the SWG waveguide are embedded in conventional taper and inverse-taper silicon waveguides to achieve polarization insensitive transmission.The proposed device has features of ultracompact,easy fabrication and low-loss,and the operation bandwidth of low loss can cover the entire wavelength range(O,E,S,C,L and U bands)of optical communication,which can be applied in optical modulators,optical switches and optical sensors.Then,an ultracompact polarization beam splitter based on Silicon Nitride/Silicon(Silicon Nitride-on-Silicon)platform is proposed and analyzed.For injected TE mode,it is coupled to adjacent waveguide by using SWG structure in bottom silicon layer,while the injected TM mode is directly transmitted along the above silicon nitride layer,where modes are guided in two separated layers independently almost without affecting each other.Meanwhile,the coupling length of proposed device is only 2.7 ?m,which has great potential applications in building ultracompact diversity schemes in PICs.Furthermore,a silicon-based ultracompact TE-pass/TM-stop power divider is proposed and analyzed in detail,where the functions of equal-power dividing and polarization selection can be integrated in single device by using SWG and segmented hybrid plasmonic horizontal slot waveguides(HPHSWs),which is beneficial to construct large scale PICs with high-integration.Results show that low-loss power dividing(TE mode)and high-efficient mode blocking(TM mode)can be obtained simultaneously in the proposed device.The insertion loss/extinction ratio for power dividing of injected TE mode/blocking of injected TM mode is 0.28 dB/19.73 dB at wavelength of 1.55 ?m,and reflection losses for TE and TM mode are-28.13 dB and-19.69 dB,respectively.Finally,the conclusion is drawn and the outlook of the future work is also presented. |
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