100 research outputs found
Hyperuniform Disordered photonic bandgap materials, from 2D to 3D, and their applications
No full textRecently, hyperuniform disordered systems attracted increasing attention due to their unique physical properties and the potential possibilities of self-assembling them. We had introduced a class of 2D hyperuniform disordered (HUD) photonic bandgap (PBG) materials enabled by a novel constrained optimization method for engineering the material's isotropic photonic bandgap. The intrinsic isotropy in these disordered structures is an inherent advantage associated with the lack of crystalline order, offering unprecedented freedom for functional defect design impossible to achieve in photonic crystals. Beyond our previous experimental work using macroscopic samples with microwave radiation, we demonstrated functional devices based on submicron-scale planar hyperuniform disordered PBG structures further highlight their ability to serve as highly compact, flexible and energy-efficient platforms for photonic integrated circuits. We further extended the design, fabrication, and characterization of the disordered photonic system into 3D. We also identify local self-uniformity as a novel measure of a disordered network's internal structural similarity, which we found crucial for photonic band gap formation. National Science Foundations award DMR-1308084
Measurement of photonic band diagram in non-crystalline photonic band gap (PBG) materials
No full textNon-crystalline PBG materials have received increasing attention recently and sizeable PBGs have been reported in quasi-crystalline structures or even in disordered structures. Band calculations for periodic structures produce accurate dispersion relations in them and refraction properties at their surfaces. However, band calculations for non-periodic structures employ large super-cells of N >100 building blocks, and provide little useful information other than the PBG frequency and width. Since band is folded into N bands, within the first Brillouin zone of the supper-cell. Using stereolithography, we construct various quasi-crystalline or disordered PBG materials and perform transmission measurements. The dispersion relations of EM wave (band diagrams) are reconstructed from the measured phase data. Our experiments not only verify the existence of sizeable PBGs in these structures, but also provide detailed information of the effective band diagrams, dispersion relation, group velocity vector, and their angular dependence. Slow light phenomena are also observed in these structures near gap frequencies. This study presents a powerful tool to investigate photonic properties of non-crystalline structures and provides important dispersion information, which is otherwise impossible to obtain
Local self-uniformity in photonic networks
No full textAbstractThe interaction of a material with light is intimately related to its wavelength-scale structure. Simple connections between structure and optical response empower us with essential intuition to engineer complex optical functionalities. Here we develop local self-uniformity (LSU) as a measure of a random network’s internal structural similarity, ranking networks on a continuous scale from crystalline, through glassy intermediate states, to chaotic configurations. We demonstrate that complete photonic bandgap structures possess substantial LSU and validate LSU’s importance in gap formation through design of amorphous gyroid structures. Amorphous gyroid samples are fabricated via three-dimensional ceramic printing and the bandgaps experimentally verified. We explore also the wing-scale structuring in the butterfly Pseudolycaena marsyas and show that it possesses substantial amorphous gyroid character, demonstrating the subtle order achieved by evolutionary optimization and the possibility of an amorphous gyroid’s self-assembly.</jats:p
Anderson localization in disordered arrays of hybrid plasmonic waveguides
No full textThe work presented here could not have been possible without the support and encouragement of my advisors, colleagues, friends, and family. I would like to express my gratitude to the members of my thesis committee, starting with my thesis advisor Dr. Huizhong Xu, whose guidance and support is largely responsible for the completion of this thesis. His endless feedback, encouragement, and patience not only made this work possible but also shaped my education and my current approach to research. Furthermore, I would like to express my appreciation to Dr. Weining Man and Dr. Maarten Golterman, not only for taking the time to read this thesis and for providing their invaluable feedback, but also for their exceptional guidance during their courses that I was privileged to take part in. I would also like to thank Dr. AKM Newaz, who was originally a member of this committee prior to his untimely passing. His warm demeanor and encouragement directed me in part towards this theoretical topic, despite being a committed experimentalist. I give thanks to the members of the nano-optics lab, not only for wonderous barbeque luncheons, but also for their camaraderie and feedback over the years. I would like to give special thanks to Dominic Ditmyer, Adam Duran, Justine Rafael, Shivam Gangwani, and Hon-Loen Sinn for their friendship, support, and herculean combined efforts during study sessions. Finally, I would like to thank my parents Shabnam and Reza for standing by me in unwavering support, and to whom I owe my curiosity and passion for science.https://doi.org/10.46569/m039kd26
Experimental demonstration waveguide with arbitrary bending angles in hyperuniform disordered photonics materials
No full textContradicting to the long standing intuition that long-range translational order is required in photonic band gap formation, recently a new class of disordered hyperuniform materials was predicted to possess sizeable photonic band gaps. We report the first experimental demonstration of complete and isotropic photonic band gap for all polarizations in such disordered hyperuniform structures made of alumina with a dielectric constant of 8.7. In periodic structures there are only a limited number of allowed rotational symmetries; hence bending angles of waveguiding channels are greatly limited. In isotropic hyperuniform disordered structures there are no preferential symmetry directions and waveguiding channels can be constructed with arbitrary bending angles. In our study, near 100 percent transmission of electromagnetic waves around sharp corners of arbitrary angles with bending radii smaller than one wavelength are observed experimentally. The hyperuniform disordered structures also enable the realization of isotropic confinement of radiation in cavities and can be used as flexible optical insulator platforms
Disordered hyperuniform photonic band gap materials
No full textUntil recently, the only materials known to have complete photonic band gaps were photonic crystals, periodic structures, and it was generally assumed that long-range periodic order was instrumental in the band gap formation. We have shown that there exists a more general class of systems, called hyperuniform photonic structures, which exhibit large and complete photonic band gaps. This classification includes not only crystalline structures, but also non-crystalline materials, ranging from quasicrystals with crystallographically-forbidden rotational symmetries to isotropic, translationally-disordered structures. Remarkably, we find that the photonic band gaps in hyperuniform disordered structures are not only comparable to those found in photonic crystals, but also display a high degree of isotropy. These new materials possess unique photonic and physical properties that provide important advantages for applications. Our results show that hyperuniform disordered structures enable the realization of optical cavities with ultimate isotropic confinement of the electromagnetic radiation, lossless waveguides with arbitrary bending angles and flexible optical insulator platforms
Freeform wave-guiding at infrared regime in two dimensional disordered photonic bandgap materials
No full textWe report the first experimental demonstration of guiding, bending and power-splitting of light in 2D disordered photonic bandgap materials at infrared wavelengths, along curved paths, around sharp bends of arbitrary angles, and through Y-shape junctions.</p
Experimental observation of photonic bandgaps in hyperuniform disordered material
No full textWe report the first experimental demonstration of photonic bandgaps (PBGs) in 2D hyperuniform disordered materials and show that is possible to obtain isotropic, disordered, photonic materials of arbitrary size with complete PBGs. There are only limited numbers of allowed rotational symmetries in periodic or quasiperiodic structures. Periodicity and Bragg scattering lead to different stop gap center frequencies in different directions, since periodicities change in different directions. Hyperuniformity together with short range geometric order and uniform local topology are enough to give raise to an isotropic PBG. Hyperuniform systems have a variance in mass or particle number which varies with distance, r, from an arbitrary point less rapidly than the d dimensional volume. We present a new class of photonic materials posessing PBGs that have a number of advantages, including: isotropy, robustness against disorder (they are already disordered), flexibility (can fit arbitrary regions of space in which one may have trouble putting a periodic system), and possibly lower minimum dielectric contrast
Some observations on hyperuniform disordered photonic bandgap materials, from microwave scale study to infrared scale study
No full textA novel class of disordered photonic materials, hyperuniform disordered solids (HUDS), attracted more attention. Recently they have been experimentally proven to provide complete photonic band gap (PBG) when made with Alumina or Si; as well as single-polarization PBG when made with plastic with refract index of 1.6. These PBGs were shown to be real energy gaps with zero density of photonic states, instead of mobility gaps of low transmission due to scattering, etc. Using cm-scale samples and microwave experiments, we reveal the nature of photonic modes existing in these disordered materials by analyzing phase delay and mapping field distribution profile inside them. We also show how to extend the proof-of-concept microwave studies of these materials to proof-of-scale studies for real applications, by designing and fabricating these disordered photonic materials at submicron-scale with functional devices for 1.55 micron wavelength. The intrinsic isotropy of the disordered structure is an inherent advantage associated with the absence of limitations of orientational order, which is shown to provide valuable freedom in defect architecture design impossible in periodical structures. NSF Award DMR-1308084, the University of Surrey's FRSF and Santander awards
Cavity modes study in hyperuniform disordered photonic bandgap materials
No full textWe introduce novel architecture for cavity design in an isotropic disordered photonic band gap material. We demonstrate that point-like defects can support localized modes with different symmetries and multiple resonant frequencies, useful for various applications.</p
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