Photonic Components Based On Silicon Photonic Crystal Nanobeam Cavities

Silicon photonics is recently fast developed as a promising integrated optoelectronics tech-nology. On one hand, it has been a long history since people learned and utilized silicon. In semiconductor industry, the commercially available technology for preparation and fabrication of silicon devices is very mature, which is beneficial to mass production of silicon photonic devices with a lower cost. On the other hand, the silicon photonic devices can be integrated with the well-developed conventional electronic devices in a monolithic substrate, thanks to their compatibility with the standard CMOS fabrication technology. The photonic devices and electronic devices can be merged in such a fashion to achieve diverse functions that they would meet the increasing de-mand for higher speed and lower power consumption. Although silicon is not an idea material for realizing the necessary active devices e.g. laser and detector, recent studies addressed these problems using the chip-bonding or epitaxy germanium technology.Silicon-on-insulator (SOI) is a large-index-contrast material platform which is very helpful for achieving ultrasmall footprint. However, the conventional silicon photonic devices are much larger than their electronic counterparts transistors, because the minimum size of traditional pho-tonic components is bounded by the diffraction limit. Photonic crystal proposed in the early90s, provides a promising alternative technology for realizing wavelength-scale or subwavelength-scale photonic components. The most achievable photonic crystal structures implemented on SOI are photonic crystal slabs and periodic dielectric waveguides. Introducing linear and point defects in such photonic crystal structures will produce so called photonic crystal waveguides and cavities, which can be further designed to form various functional devices. Compared with the photonic crystal slab cavities, periodic waveguide cavities have the advantages of ultracompact footprint, smaller mode volume and easy to fabricate and implement.This study involves the design, optimization, fabrication and characterization of ultrasmall-V high-Q nanobeam photonic crystal cavities. Our work includes mainly the following five parts:1. Based on the Maxwell solutions of a three-layer slab optical waveguide, we derived the condition for the mode confinement limit of symmetric and asymmetric tri-layer slab waveguides. The results of this part provides a theoretical baseline for engineering subwavelength mode con-finement cavities, and also contributes the design of ultracompact wave array.2. We proposed and analyzed a high-Q nanobeam periodic waveguide cavity based on hybrid-plasmonic-photonic periodic structure. Due to the deep-subwavelength mode confinement and low-loss characteristics of hbyrid-plasmonic-photonic waveguide, the designed nanobeam cavity shows a high-Q larger than2000and11times improvement of the Q/V. As far as we know, the Q factor achieved in this work stands for the highest value in such similar plasmonic cavity with so small mode volume.3. We proposed and investigated all-dielectric ultrasmall-V and ultrahigh-Q nanobeam pho-tonic crystal cavities based on slotted and hollow-core periodic dielectric waveguides. Because the strong confinement of low-index core and the discontinuity of electric field at the boundary of slot or hollow-core, Q-factors larger than105and mode volume in the order of10-2(λ/2n)3can be achieved simultaneously.4. We proposed and designed two types of channel drop filters based on the nanobeam pho-tonic crystal cavities. Using the temporal coupled mode theory, we analyzed and derived the con-ditions for reflectionless complete-dropping. Finite difference time domain method verified that the dropping efficiency is larger than99%and the typical lengthes of these two type filters are only7μm and14μm.5. Using electron beam lithography (EBL) and induced plasmon etching (IPC), we fabricated some basic nanobeam cavities components on SOI platfrom. These silicon nanobeam cavities were characterized by scanning electron microscopy and vertical fiber-grating coupling test system. These preliminary experimental work paves the way for the further study in the future.The work of this thesis mostly focus on theoretical analysis and components design, and only a few experimental work were carried out. The author hopes that the proposed components can be well verified in the future experimental study and can contribute to the ultracompact photonic compnents for future large scale photonic integration.