Browsing by Subject "Photonic crystal"
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Item Eigen value solver in C++ for a 3D photonic crystal(2006-12) Mohandas, Prakash; Chen, Ray T.A simulation study of the modes of propagation through a 3D photonic crystal using a C++ eigen value solver is presented in this work. The valid modes of propagation through a photonic crystal can be obtained by equating the field equations across the crystal boundary, which when rearranged gives rise to a complex eigen value problem. A 2D photonic crystal would yield a comparatively simple solution but the work in this thesis looks at a 3D photonic crystal which introduces a multifold of solutions. The enormity of the solution space of this problem demands that the simulation be run on a larger environment than a PC. C++ being the most compatible coding language for advanced multi processor computing systems became the obvious choice as the simulation platform. The problem of conventional computational engines such as MATLAB not having the memory capability or the speed on a PC is the primary motivation for the development of a C++ computational model. This thesis approaches the problem in multiple steps such as generating a fourier coefficient matrix for the boundary equation, solving for all the eigen values inside the crystal. The eigen values solver in this work is setup for a symmetric 3D photonic crystal. The code allows enough room for extension of the work to ultimately obtaining the valid modes in the nonsymmetric crystal.Item Embedded metallic grating and photonic crystal based scanning probes for subwavelength near-field light confinement(2012-12) Wang, Lingyun, Ph. D.; Neikirk, Dean P., 1957-; Zhang, Xiaojing, Ph. D.; Shi, Li; Yeh, Hsin-Chih; Yu, Edward T.; Alὺ, AndreaNear-field light confinement on scanning probe is the backbone technology for near-field imaging with subwavelength resolution that overcomes the diffraction limit by exploiting the properties of evanescent waves. The fusion of the photonics and the latest nanofabrication technology creates emerging frontier for near-field light confinement research with new design approach. The propagation of light can now be controlled by periodical structure at subwavelength scale with low loss in the artificially synthesized dielectric material. New light propagation patterns can now be implemented in subwavelength structure, such as directional free space light focus grating coupler, photonic bandgap material like photonic crystal by permitting light propagation at certain wavelength while prohibiting light outside of bandgap, and nano-slot light resonator for increased light-matter interaction at nanometer scale. Advances in this research area will have tremendous impact on electromagnetic modeling and biomedical technology for probe based subwavelength optical detection. My doctoral research focused on investigating highly efficient, nanofabrication compatible directional light coupling structure and near-field subwavelength light focus through photonic crystal material. The distinct significance of this research was placed on exploitation of the embedded metallic grating coupler of high free space directivity and subwavelength light processing circuit of enhanced near-field transmission rate, the two most dominating basic elements of the scanning optical imaging system. First, I designed a compact elliptical grating coupler based on embedded noble metal such as gold or silver that efficiently interconnects free space with dielectric rectangular waveguide. The dense system integration capability shows the application potential for on-chip interfacing subwavelength light processing circuits and near-field fluorescent biosensors with far-field detection of superb radiation directivity and coupling efficiency. Second, a novel all-dielectric light confinement probe designed by slotted photonic crystal waveguide provides a light confinement mechanism on the lateral plane. The resonating nano-cavities and the λ/4 nano-slot are used to enlarge the light throughput while as the nano-slot waveguide provides single subwavelength center lobe. The impetus of this research is the growing interests by near-field imaging researchers to obtain a low loss visible light confinement probe designs through mass production.Item On-chip photonic crystal waveguide for chemical and biological sensing(2013-12) Lai, Weicheng; Chen, Ray T.Photonic crystal waveguide (PCW) based device has been used in many applications in recent years due to its unique slow light effect. In this work, the application of PCW on sensing is presented. First, we present a PCW structure based Infrared (IR) spectroscopy combining with slot structure which has a large electric field enhancement for light-matter interaction for chemical sensing. The slow light effect and the electric field enhancement of our designed structure greatly enhance the absorption factor of chemical analytes by 1000. We then use multimode interference (MMI) optical splitter and Y junction combiner to connect two PCWs to show multiplexed detections of two chemicals on a single chip. Our results show the detection is down to 1 ppb for xylene in water and 100ppm for methane in nitrogen. We also present PCW microcavities structure for biological sensing in our work. Due to its high quality factor and easier immobilization of biomaterials, we are able to use ink jet printing method to bind the biomaterials on top of our chip. We choose linear-type 13 (L13, missing 13 holes) microcavities to do the biosensing for antibodies and cancer cell lysates because of its higher sensitivity combining with slow light effect. Our work achieves the cancer cell lysates detection down to 2 cells/μl., and further applications will be presented in our group in the future.Item Polymer based nano- and micro-photonic devices for three-dimensional optical interconnects(2010-12) Dou, Xinyuan; Chen, Ray T.; Bank, Seth R.; Banerjee, Sanjay K.; Lee, Jack C.; Park, Chanro; Wang, AlanThe demand for higher bandwidth and higher speed driven by semiconductor technology development draws a great deal of research efforts devoted to the development of high speed data communication. Challenges on electrical copper interconnects at high frequency make optical interconnect technologies become a promising alternative to conventional electrical interconnects at different levels. This doctoral dissertation describes polymer based nano- and micro-photonic devices for three-dimensional optical interconnects. Two areas are focused, (1) polymer based two-dimensional (2D) and three-dimensional (3D) photonic crystal fabrication and simulation for laser beam steering applications, (2) polymer based optical waveguide array and shared bus waveguide with embedded 45° micro-mirrors for board level optical interconnects. A three-dimensional (3D) face-centered cubic (FCC) type polymer based photonic crystal using the polymer material SU-8 was simulated and successfully fabricated using a polygonal prism based holographic fabrication method. The theoretical study of polymer based photonic crystals was carried out for laser beam steering, which is based on the superprism effect. Horizontally stacked two-dimensional (2D) photonic crystal was fabricated by a double exposure holographic interference method. The k-vector superprism effect, the principle for beam steering, was studied in detail through EFC (Equi-frequency Contour) analysis. A polymer based optical waveguide array with embedded 45° micro-mirrors for board level optical interconnects was prepared using a Ni metal hard mold by a UV imprint technique. A nickel based metal mold with 45º tilted surfaces on both ends of the channel waveguide was prepared through the electroplating process. To obtain a precise 45º tilted angle, a 50µm thick SU-8 layer was exposed under de-ionized water. High speed optical testing (10Gb/s) was carried out on the polymeric optical waveguide array with embedded 45º micro-mirrors on flexible substrate for out-of-plane optical interconnects. A polymer based 3-to-3 shared optical bus waveguide with opposite 45º micro-mirrors was designed and fabricated using the metallic hard mold method. The Ni metal hard mold was successfully prepared using the Ni electroplating method. This metallic hard mold provides a convenient way to fabricate the polymeric optical bus waveguide devices through the imprint technique.Item Silicon nanomembrane for high performance conformal photonic devices(2013-12) Xu, Xiaochuan; Chen, Ray T.Inorganic material based electronics and photonics on unconventional substrates have shown tremendous unprecedented applications, especially in areas that traditional wafer based electronics and photonics are unable to cover. These areas range from flexible and conformal consumer products to biocompatible medical devices. This thesis presents the research on single crystal silicon nanomembrane photonics on different substrates, especially flexible substrates. A transfer method has been developed to transfer silicon nanomembrane defect-freely onto glass and flexible polyimide substrates. Using this method, intricate single crystal silicon nanomembrane device, such as photonic crystal microcavity, has been transferred onto flexible substrates. To test the device, subwavelength grating couplers are designed and implemented to couple light in and out of the transferred waveguides with high coupling efficiency. The cavity shows a quality factor ~ 9000 with water cladding and ~30000 with glycerol cladding, which is comparable to the same cavity demonstrated on silicon-on-insulator platform, indicating the high quality of the transferred silicon nanomembrane. The device could be bended to a radius less than 15 mm. The experiments show that the resonant wavelength shifts to longer wavelength under tensile stress, while it shifts to shorter wavelength under compressive stress. The sensitivity of the cavity is ~70 nm/RIU, which is independent of bending radius. This demonstration opens vast possibilities for a whole new range of high performance, light-weight and conformal silicon photonic devices. The techniques and devices (e.g. wafer bonding, stamp printing, subwavelength grating couplers, and modulator) generated in the research can also be beneficial for other research fields.