Silicon Photonic Integrated Devices Based On Waveguide Gratings

Bragg grating is a very important optical device, which has achieved great success in optical fiber communication. With the rapid development of silicon photonics, Bragg grating becomes a new integrated photonic device. Since advantage of the CMOS compatible fabrication processes, silicon-on-insulator (SOI) is the most promising platform for integrated photonic devices. Bragg gratings based on SOI platform have some advantages over fiber Bragg gratings, such as compact footprint, low cost and so on. Silicon Bragg gratings have been widely studied and applied in active and passive optical devices e.g. lasers, couplers, splitters, polarization isolators, add-drop filters and optical sensors. As the various demand of the integrated optics, it is still a challenging subject to study the silicon Bragg grating based devices.This paper focuses on the silicon Bragg grating and Bragg grating assisted couplers. This thesis makes innovative works mainly in the aspects as follows:1. A narrow bandwidth filter is demonstrated. The filter is based on slab-modulated sidewall Bragg gratings in SOI ridge waveguide. This design enables precise control and a wide dynamic range of coupling srength and bandwidths. The band widh of the uniform structure and the sample structure are2.9nm and0.4nm, respectively.2. A slab-modulated sidewall Bragg gratings in SOI ridge slot waveguide with tunable coupling coefficient and large fabrication tolerance, is proposed and designed. With a slot filled with electro-optic (EO) polymer, its resonant wavelength can be linearly tuned by first-order EO effect with a high sensitivity of332nm/RIU.3. A novel apodized cladding modulated Bragg grating is presented. The coupling strength is varied by modulating the distance between the rectangulars and the waveguide. Calculated results show that the sidelobe of the grating is restrain lower than-30dB.4. An add-drop filter based on silicon grating-assisted contradirectional couplers is designed and analysed, with the resonant wavelength of1538nm, the3dB bandwidth of7nm and the extinction of22dB.An add-drop filter with an unlimited free spectral range (FSR) is also proposed. The intrawaveguide coupling is significantly diminished by distancing the periodically structured corrugated waveguide away from the straight input waveguide. Based on this asymmetric structure, calculated results show that the peak reflectivity of the intrawaveguide coupling is lower than0.1dB, while that of the contradirectional coupling is higher than20dB. An experimental result of1.8dB for the intrawaveguide coupling is obtained.5. A simple and low-crosstalk1×4silicon mode (de)multiplexer based on multimode grating-assisted-couplers is proposed. Mode transitions can be flexibly controlled by designing the grating period at the phase-matching condition. Due to the contra-directional coupling, precise control of the coupling strength and the coupling length are not needed in the system. A simple multimode grating assisted coupler is also designed. Experimental results show that the the3dB bandwidths and extinction ratios of the device are0.75nm and7dB,1.3nm and18dB for the mode transitions from single mode waveguide to the1st and2nd of the multimode waveguide.