Browsing by Subject "Photonic crystals"
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Item Advanced lithographic patterning technologies : materials and processes(2007-05) Taylor, James Christopher, 1980-; Willson, C. G. (C. Grant), 1939-Immersion lithography has emerged as the next technology to achieve the resolution improvement needed to produce smaller and faster microelectronic devices. It involves filling the air gap between the lens and photoresist-coated silicon wafer in a lithographic exposure tool with a higher refractive index medium. This improves the coupling of light into the resist and allows for better resolution. At the current exposure wavelength of 193 nm, water has been identified as the most promising immersion medium. Several potential issues had to be resolved before the process would be adopted. One was the unknown consequence of intimate contact between water and a photoresist. Any extraction of small molecule photoresist components by water could lead to a degradation of imaging performance and/or contamination. To address this, the possible extraction of several examples of these components from model 193 nm photoresists was studied by multiple experimental techniques including liquid chromatography/mass spectroscopy, scanning electrochemical microscopy and radiochemical analysis. It was found that both a photoacid generator and a base additive were extracted in small quantities. A study of the optical properties of water-based solutions with ionic additives was then undertaken. This study was intended to identify fluids with a higher index than water for greater resolution improvement. The solutions had higher index values, though typically with prohibitively high absorbance. The survey did lead to a series of methylsulfonate salts with some of the highest index values paired with low absorbance found for these materials. However, none of the target fluid properties were reached, so a theoretical approach was then used to model the properties of an ideal additive. This model served as a guide to identify a new type of additive with both a high index and low absorbance. The principles used for a high index/low absorbance additive were then applied to fabricate a polymer photonic device. A photonic crystal structure was designed for a polymer with an additive. A process for fabricating it was then developed using step and flash imprint lithography. The process development included a demonstration of a template created with a negative tone electron beam lithography process.Item Advanced lithographic patterning technologies: materials and processes(2007) Taylor, James Christopher; Willson, C. G. (C. Grant), 1939-Immersion lithography has emerged as the next technology to achieve the resolution improvement needed to produce smaller and faster microelectronic devices. It involves filling the air gap between the lens and photoresist-coated silicon wafer in a lithographic exposure tool with a higher refractive index medium. This improves the coupling of light into the resist and allows for better resolution. At the current exposure wavelength of 193 nm, water has been identified as the most promising immersion medium. Several potential issues had to be resolved before the process would be adopted. One was the unknown consequence of intimate contact between water and a photoresist. Any extraction of small molecule photoresist components by water could lead to a degradation of imaging performance and/or contamination. To address this, the possible extraction of several examples of these components from model 193 nm photoresists was studied by multiple experimental techniques including liquid chromatography/mass spectroscopy, scanning electrochemical microscopy and radiochemical analysis. It was found that both a photoacid generator and a base additive were extracted in small quantities. A study of the optical properties of water-based solutions with ionic additives was then undertaken. This study was intended to identify fluids with a higher index than water for greater resolution improvement. The solutions had higher index values, though typically with prohibitively high absorbance. The survey did lead to a series of methylsulfonate salts with some of the highest index values paired with low absorbance found for these materials. However, none of the target fluid properties were reached, so a theoretical approach was then used to model the properties of an ideal additive. This model served as a guide to identify a new type of additive with both a high index and low absorbance. The principles used for a high index/low absorbance additive were then applied to fabricate a polymer photonic device. A photonic crystal structure was designed for a polymer with an additive. A process for fabricating it was then developed using step and flash imprint lithography. The process development included a demonstration of a template created with a negative tone electron beam lithography process.Item Fabrication and process optimization for functional 3D periodic nanolattices(2023-12) Premnath, Vijay Anirudh; Chang, Chih-Hao, Ph. D.This research focuses on the development and analysis of advanced nanolattices and three-dimensional (3D) nanostructures, showing their significance in nanophotonics, integrated circuits, lasers, optical systems, and various other applications. Nanolattices are characterized by their periodic lattice arrangement, hollow-core, and thin-shell elements, are fabricated using thin-film deposition on 3D polymer templates. These structures offer immense potential in mechanical, optical, and thermal applications, due to their unique properties. However, a major challenge in their fabrication is the residual polymer left within the nanolattice, which can impede their performance. To address this, the study investigates three different polymer template removal techniques, including oxygen plasma etching, solvent dissolution, and thermal desorption, to determine their effectiveness in eliminating residual polymer. The removal rates and effectiveness of each method are quantitatively analyzed using spectroscopic ellipsometry, a technique that precisely measures the effective refractive index and calculates the amount of residual polymer. The findings reveal that thermal treatment is the most effective in template removal, providing a path to enhance nanolattice fabrication for various applications. Additionally, the research utilizes a three-phase Maxwell–Garnett effective medium model to estimate the residual polymer in nanolattices. Parallelly, the research delves into the fabrication of 3D nanostructures, specifically opal structures, which are spatially aligned to an array of holes defined in the photoresist. This approach employs colloidal lithography to pattern a hexagonal array of holes, guiding the assembly of colloidal particles into 3D opal structures. This method ensures the alignment of the 3D opal structures with the 2D hole array, enhancing spatial-phase coherence and minimizing defects. The polymer patterns serve as a sacrificial template for atomic layer deposition, enabling the creation of free-standing nanolattices. These nanolattices are subsequently coated with a thick layer of titanium oxide, demonstrating their mechanical stability. The resulting structures boast high porosity, essential for creating low-index materials in nanophotonics. Additionally, the study incorporates nature-inspired nanostructures, employing biomimetic principles to enhance the functionality and efficiency of these materials. These nature-inspired designs, mimicking the structures found in natural organisms, provide solutions for light manipulation and structural resilience. These nanostructures, with controlled height and precise deposition, are ideal for applications in Bragg reflectors, nanophotonics, and optical multilayers, marking a significant advancement in the field of nanostructured materials. The study's findings on template removal, 3D nanostructure fabrication, and biomimetic design open new avenues for research and development in this rapidly evolving field, promising enhancements in the efficiency and functionality of nanostructured materials and devices.Item Optical effects in photonic crystals and metamaterials(2011-05) McIlhargey, James Garland; Shvets, G.; Li, XiaoquinIn this thesis, I will describe the polarization properties of two separate but similar optical systems. I will begin by showing anisotropy in a dielectric photonic crystal slab patterned with a periodic circular hole array. This anisotropy can be utilized in manipulating the gain properties of surface emitting photonic crystal lasers. I will then describe a metallic, planar metamaterial patterned similarly with a 2d periodic array of holes. The enhanced optical transmission of this system is demonstrated computationally and experimentally, with a good agreement between the two. I will also demonstrate polarization rotation in this array. The effect is shown to minimize the background contribution to the transmission resulting in the narrowing of the line width and improvement between on and off resonance contrast. I then provide a theory behind the polarization rotation in transmission through a metamaterial based upon a Jones matrix formulation, which is dependent only upon the existence of separate s and p resonances in a photonic system.Item Silicon - polymer hybrid integrated microwave photonic devices for optical interconnects and electromagnetic wave detection(2015-05) Zhang, Xingyu, 1986-; Chen, Ray T.; Willson, Grant; Alu, Andrea; Akinwande, Deji; Poggio, EnricoThe accelerating increase in information traffic demands the expansion of optical access network systems that require high-performance optical and photonic components. In short-range communication links, optical interconnects have been widely accepted as a viable approach to solve the problems that copper based electrical interconnects have encountered in keeping up with the surge in the data rate demand over the last decades. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for integrated photonic applications to support futuristic data communication networks. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power active photonic devices. Beside board level passive and active optical components, on-chip micro- or nano-photonic devices have been made possible by the hybrid integration of EO polymers onto the silicon platform. In recent years, silicon photonics have attracted a significant amount of attentions, because it offers compact device size and the potential of complementary metal–oxide–semiconductor (CMOS) compatible photonic integrated circuits. The combination of silicon photonics and EO polymers can enable miniaturized and high-performance hybrid integrated photonic devices, such as electro-optic modulators, optical interconnects, and microwave photonic sensors. Silicon photonic crystal waveguides (PCWs) exhibit slow-light effects which are beneficial for device miniaturization. Especially, EO polymer filled silicon slotted PCWs further reduce the device size and enhance the device performance by combining the best of these two systems. The potential applications of these silicon-polymer hybrid integrated devices include not only optical interconnects, but also optical sensing and microwave photonics. In this dissertation, the design, fabrication, and characterization of several types of silicon-polymer hybrid photonic devices will be presented, including EO polymer filled silicon PCW modulators for on-chip optical interconnects, antenna-coupled optical modulators for electromagnetic wave detections, and low-loss strip-to-slot PCW mode converters. In addition, some polymer-based devices and silicon-based photonic devices will also be presented, such as traveling wave electro-optic polymer modulators based on domain-inversion directional couplers, and silicon thermo-optic switches based on coupled photonic crystal microcavities. Furthermore, some microwave (or RF) components such as integrated broadband bowtie antennas for microwave photonic applications will be covered. Some on-going work or suggested future work will also be introduced, including in-device pyroelectric poling for EO polymer filled silicon slot PCWs, millimeter- or Terahertz-wave sensors based on EO polymer filled plasmonic slot waveguide, low-loss silicon-polymer hybrid slot photonic crystal waveguides fabricated by CMOS foundry, logic devices based on EO polymer microring resonators, and so on.Item Silicon integrated nanophotonic devices for on-chip optical interconnects(2012-05) Lin, Che-Yun; Chen, Ray T.; Bank, Seth R.; Willson, Carlton G.; Lee, Jack C.; Alu, Andrea; Wang, Alan X.Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research.Item Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications(2017-06-07) Williamson, Ian Alexander Durant; Wang, Zheng, Ph. D.; Alù, Andrea; Bank, Seth R; Wang, Yaguo; Yu, Edward TThis dissertation is organized into three parts. First, the design for a radio frequency fiber transmission line built out of a grid of micrometer-scale conductors embedded in an insulating polymer cladding is presented to mitigate the skin and proximity effects. By adopting a checkerboard out-of-phase current phasing scheme, the internal inductance of the line is significantly lower than in two-conductor lines and results in an LC bandwidth of approximately 2 GHz, with flat attenuation and linear phase dispersion. The device performance is characterized in terms of its geometric degrees of freedom and a fabricated prototype is presented. Second, the kinetic inductive and plasmonic response of monolayer graphene in the terahertz spectrum is examined in the context of several important applications. The dispersive responses of two-dimensional graphene and three-dimensional copper transmission lines are compared to map the dispersive signaling performance in terms of transmission line cross-sectional size. This demonstrates a surprisingly broadband LC response with flat attenuation in nano-scale lines. This kinetic inductive response of graphene is demonstrated to miniaturize the photonic band structure of a photonic crystal slab where an in-plane periodicity of 300 nm has its photonic band gap in the terahertz spectrum. The sub-diffraction photonic band structure resembles that of the two-dimensional photonic crystal, supporting a wide photonic band gap in extremely thin slabs. The viability of graphene for cavity optomechanics is analyzed from near infrared to terahertz wavelengths, demonstrating a large optomechanical coupling, on the order of 3D optomechanical materials. Third, a class of nonreciprocal devices is proposed based on coupling to the sideband states, called Floquet resonances, that arise in temporally modulated optical resonators. The degrees of freedom in the modulating waveform tailor the energy exchange and phase of the Floquet resonances to realize unique nonreciprocal spectral responses in compact devices. We examine optical scattering from Floquet resonators coupled to narrowband waveguides using temporal coupled-mode theory. A three-port circulator is built out of a cascade of Floquet resonators to demonstrate broadband forward transmission and ideal isolation for dual-carrier waves. Full-wave numerical simulations in the coupled frequency domain demonstrate the circulator in an on-chip photonic crystal platform