Research On Silicon-Based Photonic Crystal Band Gap And Waveguide

With the fast increasing of microelectronic devices integration in a single silicon chip, device fabrication line width is approaching to the theoretical limit. Therefore, microelectronics technology which uses electrons as information carriers will soon face formidable bottleneck. Thus, optoelectronics integration which uses photons as the information carrier is thought to be the new development direction. Silicon based photonic crystal, which inherits of the mature silicon processing technology of modern large scale integrated circuits and also has the perfect ability to control light due to their photonic band gap, naturally becomes to be the research hotspot. Silicon based photonic waveguides is the information transmission channel, and also is one of the key foundation devices for silicon-based integrated optical circuits. In the basis of the silicon based photonic crystal waveguide, a variety of different functions silicon-based optoelectronic devices can be designed and fabricated, such as silicon-based micro-cavity, waveguide, optical delay, splitter, couplers, modulators, detection and so on. Therefore, supported by the National Basic Research Program of China (grant 2006CB708310), Natural Science Foundation of China (grant 60706013), Natural Science Foundation of Hubei (grant 2006ABD002), the Independent Creative Research Foundation of Huazhong University of Science and Technology (grant M2009026), the Creative Research Foundation of Wuhan National Laboratory for Optoelectronics (grant P080003) and the Graduation Creative Research Foundation of Huazhong University of Science and Technology(grant HF-08-05-2011-230), this thesis focus on the photonic band gap characteristic and new types of silicon based photonic crystal waveguide devices:(1) Based on investigations and discussions of the formation mechanism of photonic band gap in photonic crystal, photonic band structures of annular photonic-crystal silicon-on-insulator asymmetric slabs with finite thickness were investigated by the three-dimensional plane-wave expansion method. The results show that for a broad range of air-volume filling factors, annular photonic-crystal slabs can exhibit a significantly larger band gap than conventional circular-hole photonic-crystal slabs. For a noticeable case, approximately a two-fold enhancement of the band gap was observed based on the same configurations except the use of optimized annular holes instead of circular holes. This desirable behavior suggests a potential for annular photonic-crystal silicon-on-insulator slabs to serve as the basis of various optical cavities, waveguides, and mirrors.(2) Based on the investigations and discussion of the flat band slow light mechanism in photonic crystal waveguide, flat band low dispersion slow light in symmetric line defect photonic crystals waveguide formed by adding dielectric pillars in the air holes nearest to the waveguide core is investigated. By adjusting the radii of the new dielectric pillars, a linear band in the photonic band structure appears which denotes low group velocity dispersion. High average group index of 74.4 with 2.3 nm bandwidth centered at 1550 nm wavelength is demonstrated in an optimized waveguide by finite-difference time-domain simulation. The novel photonic crystal waveguide can provide various applications, such as optical buffer memories, efficient optical switches and especially in enhanced light-matter interaction both in the linear and nonlinear regime with a simple and straight structure.(3) Based on the investigations and discussion of dispersion compensation wide band slow light mechanism in photonic crystal waveguide, wideband dispersion-free slow light in chirped-slot photonic-crystal coupled waveguides is proposed and theoretically investigated in detail. By systematically analyzing the dependence of band shape on various structure parameters, unique inflection points in the key photonic band with approximate zero group velocity can be obtained in an optimized slot photonic-crystal coupled waveguide. By simply chirping the widths of the photonic-crystal waveguides in the optimized structure, wideband (up to 20 nm centered at 1550 nm wavelength) slow-light with optical confinement in the low dielectric slot is demonstrated numerically with relative temporal pulse-width spreading well below 8% as obtained from two-dimensional finite-difference time-domain simulations. The wideband slow-light operation of the proposed structures would offer significant potential for novel compact high-speed optical-signal-processing devices in silicon-based systems.(4) Based on the investigations and discussion of photonic crystal self-collimation phenomena and theory, making use of the two freedom adjustable parameters of the annular photonic crystal, the frequency bands for self-collimation at both TE and TM polarizations in square lattice annular photonic crystals are studied systematically by plane wave expansion and finite difference time domain methods. A polarization insensitive self-collimation waveguide in a high dielectric contrast system with bandwidth up to 102.9 nm is demonstrated as an example of the implementation of photonic integration circuits.