Compact silicon-based wavelength-selective photonic integrated devices and the applications

In wavelength-division multiplexing systems, it is important to develop various wavelength-selective components to have flexible and reconfigurable nodes. When using conventional optical waveguides with low index contrast, the sizes of these wavelength-selective components are usually several cm(2), which is too large to integrate more components in a single wafer or chip. In order to improve the integration density and reduce the cost, it is desirable to minimize the component sizes. In our case, two kinds of strongly-confined optical waveguides on silicon wafer are considered for compact wavelength-selective devices. One is the popular silicon-on-insulator (SOI) nanowire and the other is SU-8 strip optical waveguide with an air cladding and a SiO2 insulator layer on a Si substrate. In this paper, we give a review of our recent work on wavelength-selective photonic integrated devices based on these two kinds of silicon-based optical waveguides with strong-confinements. Arrayed-waveguide grating (AWG) and microring resonator (MRR), which are two typical wavelength-selective components are included. First we give a review for several new layouts for SOI-nanowire AWG to have a further size-reduction and our novel designs for diminishing the polarization dependency of AWGs. Secondly we present the design and fabrication of multimode interference (MMI) couplers for MRRs. A novel design method for tapered MMI couplers is presented and the diminishment of polarization in a MMI coupler is proposed by optimizing the tapered MMI section. We also present our experimental results on optical sensor combining MRRs and micro-fluid channel. The measured sensitivity is about 180nm/RIU.