Optically-resonant nanostructure-based systems for spectral selectivity

This thesis presents two different approaches for spectrally-selective nanostructure-based systems with their specific advantages and disadvantages; see Chapter 1 for spectrally-selective Mie-resonant metasurfaces, and Chapter 2 for nanostructure-modulated FP resonators. Furthermore, to bridge the gap between fundamental science and industry, novel fabrication techniques laser-induced tailoring and structuring of metasurfaces are presented; see Chapter 3. All things considered, this work is not intended to revolutionize optics. Still, it is written with a bit of hope to put a small step in the development of nanophotonics and its applicability in real-world applications

Polymer-based 3-D printing of G-band metal-pipe rectangular waveguide components

The objective of this thesis is to investigate the use of low-cost polymer-based 3-D printing for G-band (140 to 220 GHz) metal-pipe rectangular waveguide (MPRWG) components. First, various preliminary designs are investigated. Then, a successful ‘trough-and-lid’ assembly is demonstrated, which mitigates against the main design challenges for split-block waveguide construction at upper-millimeter-wave frequencies (ca. 100 GHz to 300 GHz), and can be realized using low-cost 3-D printing and conventional metal plating techniques. With this assembly, inexpensive masked stereolithographic apparatus (MSLA) 3-D printers and a standard commercial copper electroplating service are used. The trough-and-lid assembly is expected to provide a standard solution for the low-cost and low loss realization of most MPRWG implementations above 100 GHz; previously, this was infeasible without the use of high-cost, state-of-the-art 3-D printing and/or custom-developed metal plating techniques. Three different component types are successfully demonstrated: (i) straight thru lines; (ii) 90° twists; and (iii) bandpass filters (BPFs). Along with frequency-domain S-parameter measurements, a detailed time-domain reflectometry analysis is also included. For the more accurate characterization of these components, the additional insertion loss due to conductor surface roughness is investigated. Finally, the integration of an MPRWG component into a millimeter-wave subsystem, which is based on the design of a radiometer front-end, is presented.Open Acces

High-Q Fused Silica Micro-Shell Resonators for Navigation-Grade MEMS Gyroscopes

This research aims to develop the resonator for a navigation-grade microelectromechanical system (MEMS) Coriolis vibratory gyroscope (CVG) that will bring inertial navigation capabilities to a wider range of applications by reducing gyroscope size and cost. To achieve the desired gyroscope performance, the gyroscope resonator must have low energy dissipation and a highly symmetric structure. Several challenges arise at the micro-scale due to the increased sensitivity to imperfections and increased susceptibility to energy loss mechanisms. This work investigates the lower limit on energy dissipation in a micro-shell resonator known as the birdbath (BB) resonator. The BB resonator is designed to mitigate the energy loss mechanisms that commonly limit MEMS resonators, including anchor loss and thermoelastic dissipation, through a unique shape and fabrication process and through the use of fused silica as the structural material. A blowtorch molding process is used to form high aspect ratio fused silica shells with a range of wall profiles, providing a high level of control in three dimensions that is not possible with conventional micromachining techniques. Prototype BB resonators were developed prior to this dissertation work but they achieved low quality factors (Q) and low ring-down time constants (T) on the order of 100 thousand and 1 s, respectively. The goal of this work is to drastically increase performance above these initial results. Each relevant energy loss mechanism is considered in order to identify the dominant loss mechanism for a given device. Process improvements are implemented to mitigate each loss mechanism, including improved thermal management during blowtorch molding, cleaner lapping and polishing, reduced upfront surface contamination, and methods to remove contaminants after fabrication. Following optimization, Qs up to 10 million and Ts up to 500 s are measured, representing a marked improvement over the prototype resonators. It is found that BB resonators are now limited by surface loss, as indicated by the observed inverse relationship between Q and surface-to-volume ratio. The surface-loss-limited regime results in a high sensitivity to added surface layers. The addition of a conductive layer to enable electrostatic transduction is found to have a large impact, decreasing Q by 50% with the addition of only 30 angstroms of metal. It is suggested that the origin of this loss may be interfacial slippage due to a large increase in stress that occurs at the interface during oscillation. Experimental investigation into the dependence of Q on conductive layer composition, thickness, deposition conditions, and post-deposition treatments is carried out. Following treatments to removed adsorbed contaminants from the surface, resonators with a 15/50 angstrom Ti/Pt layer are found to maintain 60% of their initial Qs. Indium tin oxide (ITO) is identified as a promising conductive layer candidate, with initial experiments producing shells that maintain 70% of their initial Q. The values of Q and T produced in this work are unprecedented for MEMS resonators. Even accounting for the losses that accompany conductive layer deposition, birdbath resonator gyroscopes are expected to achieve navigation-grade performance.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146096/1/taln_1.pd

Developing highly symmetric Microelectromechanical systems (MEMS) based butterfly gyroscopes

Microelectromechanical systems (MEMS) is the technology combining electrical components with mechanical systems at a micro scale. The combination of these two technologies allowed devices to interact with each other and build complex structures. System on the chips are built with components such as masses, electrodes, anchors, actuators and detectors. Reducing the size, weight, energy usage and cost is key while maintaining the sensors integrity. Sensitivity is an important factor when evaluating a gyroscope’s performance. This research presents beam modeling techniques for maximizing mechanical sensitivity of the butterfly resonator for gyroscopic applications. It investigates the geometric aspects of synchronizing beam that connects the wings of a butterfly resonator. The results show that geometric variation in the synchronizing beam can have a large effect on the frequency split and sensitivity of the device. The model simulation demonstrates a sensitivity of 10e-12 (m/°/sec) for a frequency split of 10 Hz, resulting from the optimized synchronous beam. Out of plane actuation was developed to drive and sense the resonators displacement. A butterfly sensor chip was fabricated to capture the dynamic responses of the resonator and to observe the theoretical and experimental results. Two butterfly resonators were tested, and the experimental results show a frequency split of 305 Hz and 400 Hz, while the model illustrated a split of 195 Hz and 220 Hz, respectively. The design and analysis presented in this thesis can further aid the development of MEMS butterfly resonators for inertial sensing applications

Nanophotonic split-ring resonators as dichroics for molecular spectroscopy

The unique optical properties of metallic nanostructures have enabled the creation of a new generation of ultra sensitive biosensors based on vibrational spectroscopy. Through strict engineering of structural morphology, a nanometal’s free electrons can be tuned to resonate at a particular frequency, resulting in amplification and confinement of the electromagnetic field around certain areas of the structure. Molecules situated within these areas experience a greater degree of polarisation due to the oscillating plasmon field, a phenomena which, when combined with resonance Raman spectroscopy, has been shown to enable single molecule detection.1, 2 This thesis describes the fabrication and plasmonic characterisation of Au and Ag circular nano split-ring resonators using a combination of electron beam lithography, finite difference time domain simulation and transmission spectroscopy. Through alteration of ring radius, arc length, wall width, metal thickness and metallic composition it is shown that the asymmetric split-ring structures exhibit a multi-modal, polarisation dependent plasmonic response that can be tuned over several microns. Such a response enables these geometries to be employed as novel multi-wavelength biosensors via surface enhanced Raman spectroscopy and surface enhanced resonance Raman spectroscopy. This work goes on to demonstrate that by using electron beam lithography to manipulate the nano-scale geometry of Ag split-ring resonators, their optical properties can be tuned such that the structures exhibit two independently addressable, high frequency plasmon resonance modes for SERRS. In a series of sensing experiments it is shown that this tailored, multi-modal, polarisation dependent activity enables the split-rings to act as discriminating sensors, with each resonance tuned for a particular sensing purpose. Ultimately the structures are used as multi-wavelength, multi-analyte DNA SERRS sensors, with each resonance tuned both to the absorption wavelength of a differently coloured Raman reporter molecule and its corresponding laser excitation wavelength. In doing so, the ability of each resonance to independently sense clinically relevant concentrations of single DNA strand types from within a mixed population on the sensor surface is demonstrated

Nanoengineered Functional Structures for Photonic and Microfluidic Applications

Owing to their extraordinary ability to interacting with external stimuli as well as their versatile functionalities hardly observed in bulk systems, micro- and nano-scale materials, structures, and phenomena have been the subject of increasing interest from both academia and industry. Many diverse fields including optoelectronics, photonics, bioengineering, and energy conversion have all shown significant increases in utilization of, and need for, micro/nano-scale features. To meet this demand, not only novel manufacturing methodologies, but also underlying physics and design principles are called for. This thesis work addresses these issues while focusing on three main topics: (1) how certain fundamental nanostructures such as periodic nanopatterned surface, multilayers and charged particle-line can be utilized as functional building blocks for multidisciplinary applications ranging from nanoparticle/biomolecule manipulation to optoelectronics/photonics; (2) how these functional nanoarchitectures can be engineered in a continuous and scalable manner to increase the manufacturing throughput; and (3) the underlying physics and the design principles of these nanostructures in particular application systems. More specifically, large area, 1D/2D periodic sinusoidal nanopatterned surface based on Dynamic Nano-inscribing (DNI) patterning technique is developed. And its applications to nanoparticle assembly/sorting and light extraction from GaN LED are investigated. By exploiting this sinusoidal nanovoid pattern and geometry-dependent ionic entropy, we successfully realized the size-selectively confinement and patterning of submicron-sized particles over a large area. Moreover, general method of light extraction from trapped modes by using these 1D/2D sinusoidal nanogratings have been developed. We applied our method to flip-chip GaN LED and a further enhancement of the total radiative power in addition to the PSS structures have been observed. Metal/dielectric multilayer structures are widely used as fundamental building blocks for photonic crystal/metamaterials, color filters and anti-reflection coatings. Here in this work, we are focus on the applications of metal/dielectric multilayers on hyperbolic metamaterials (HMM) and surface-plasmon-coupled light emission from 2D materials and organic light emission materials. For hyperbolic metamaterials, we show that by using thin (~7nm) Al doped Ag metal films, we can dramatically improve the performance as well as the photon density of state (DOS) of the HMM. However, a further discussion on the nonlocal response of electrons in ultrathin (sub-1nm) metal films have been conducted and shows that the nonlocality induced by quantum effects of electrons (degeneracy pressure, diffusion kinetics and tunneling) can dramatically induce the transitions of the photonic topology of the metamaterials and intrinsically limit the DOS. Metal/dielectrics multilayers are also used to study the exciton-plasmon energy transfer and surface plasmon coupled light emission from 2D semi-conductors (WSe2) and organic light emission materials (Super Yellow). Based on one optimized planar multilayer structure we observed an 8 times enhancement of the PL signal. And we applied this concept to OLED structure, enhancement of the efficiency were also observed from SY-based OLEDs.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137153/1/lonchen_1.pd

The left hand of electromagnetism : metamaterials

Ankara : The Department of Physics and the Institute of Engineering and Science of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 160-172.Metamaterials are artificial periodic structures whose electromagnetic response is solely dependent on the constituting unit cells. In the present thesis, we studied unit cell characteristics of metamaterials that has negative permeability and permittivity. We investigated negative permeability medium elements, especially in terms of their electrical size and resonance strength. Experimental and numerical study of µ-negative (MNG) materials: multi split ring resonators (MSRRs), spiral resonators (SRs) and multi-spiral resonators are presented. The resonance frequency of the structures is determined by the transmission measurements and minimum electrical size of λ0/17 for the MSRRs and of λ0/82 for the SRs observed. We explain a method for tuning the resonance frequency of the multi-split structures. We investigated scalability of MNG materials and designed a low loss double negative composite metamaterial that operates at the millimeter wave regime. A negative pass-band with a peak transmission value of -2.7 dB was obtained experimentally at 100 GHz. We performed transmission based qualitative effective medium theory analysis numerically and experimentally, in order to prove the double negative nature of the metamaterial. These results were supported by the standard retrieval analysis method. We confirmed that the effective index of the metamaterial was indeed negative by performing far field angular scanning measurements for a metamaterial prism. Moreover, we illuminated the split-ring resonator based metamaterial flat lens with oblique incidence and observed from the scanning experiments, the shifting of the beam to the negative side. The first device was a horn antenna and metamaterial lens composite whose behavior was similar to Yagi-Uda antenna. We numerically and experimentally investigated planar fishnet metamaterials operating at around 20 GHz and 100 GHz and demonstrated that their effective index is negative. The study is extended to include the response of the metamaterial layer when the metamaterial plane normal and the propagation vector are not parallel. We also experimentally studied the transmission response of a one dimensional rectangle prism shaped metamaterial slab for oblique incidence angles and confirmed the insensitivity of split-ring resonator based metamaterials to the angle of incidence. After the demonstration of complete transmission enhancement by using deep subwavelength resonators into periodically arranged subwavelength apertures, we designed and implemented a metamaterial with controllable bandwidth. The metamaterial based devices can be listed under the categories of antennas absorbers and transmission enhancement. We studied electrically small resonant antennas composed of split ring resonators (SRR) and monopoles. The electrical size, gain and efficiency of the antenna were λ0/10, 2.38 and 43.6%, respectively. When we increased the number of SRRs in one dimension, we observed beam steerability property. These achievements provide a way to create rather small steerable resonant antennas. We also demonstrated an electrically small antenna that operates at two modes for two perpendicular polarizations. The antenna was single fed and composed of perpendicularly placed metamaterial elements and a monopole. One of the metamaterial elements was a multi split ring resonator and the other one was a split ring resonator. When the antenna operates for the MSRR mode at 4.72 GHz for one polarization, it simultaneously operates for the SRR mode at 5.76 GHz, but for the perpendicular polarization. The efficiencies of the modes were 15% and 40% with electrical sizes of λ/11.2 and λ/9.5. Finally, we experimentally verified a miniaturization method of circular patch antennas. By loading the space between the patch and ground plane with metamaterial media composed of multi-split ring resonators and spiral resonators, we manufactured two electrically small patch antennas of electrical sizes λ/3.69 and λ/8.26. The antenna efficiency was 40% for the first mode of the multi-split ring resonator antenna with broad far field radiation patterns similar to regular patch antennas. We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of i) a metal back plate and an artificial magnetic material layer; ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a λ/4.7 thick absorber of type i), with a 99.8% absorption peak along with a 8% fractional bandwidth. We have also demonstrated experimentally a λ/4.7 and a λ/4.2 thick absorbers of type ii), based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. We conveyed these concepts to optical frequencies and demonstrated a metamaterial inspired absorber for solar cell applications. We finalized the study by a detailed study of split ring resonators at the infrared and visible band. We studied i) frequency tuning, ii) effect of resonator density, iii) shifting magnetic resonance frequency by changing the resonator shape, iv) effect of metal loss and plasma frequency and designed a configuration for transmission enhancement at the optical regime. By using subwavelength optical split ring resonator antennas and couplers we achieved a 400-fold enhanced transmission from a subwavelength aperture area of the electrical size λ2 /25. The power was transmitted to the far field with 3.9 dBi directivity at 300 THz.Alıcı, Kamil BoratayPh.D

Technologies for single chip integrated optical gyroscopes

Optical gyroscopes are being employed for navigational purposes for decades now and have achieved comparable or better reliability and performance than rotor-based gyroscopes. Mechanical gyros are however generally bulky, heavy and consume more power which make them unsuitable for miniaturized applications such as cube satellites and drones etc. Therefore, much effort is being expended worldwide to fabricate optical gyros having tactical grade robustness and reliability, small size, weight, cost and power consumption with minimal sacrifice of sensitivity. Integrated optics is an obvious approach to achieving this. This work comprises detailed comparative analysis of different types and structures of integrated optical gyroscopes to find out the suitable option for applications which require a resolution of <10 o/h. Based on the numerical analysis, Add-drop ring resonator-based gyro is found to be a suitable structure for integration which has a predicted shot noise limited resolution of 27 o/h and 2.71 o/h for propagation losses of 0.1 dB/cm and 0.01 dB/cm respectively. An integrated gyro is composed of several optical components which include a laser, 3dB couplers, phase/frequency modulators, sensing cavity and photodetectors. This requires hybrid integration of multiple materials technologies and so choices about which component should be implemented in which technology. This project also undertakes theoretical optimization of few of the above-mentioned optical components in materials systems that might offer the most convenient/tolerant option, this including 3dB coupler, thermo-optic phase modulator and sensing cavity (resonator and waveguide loop). In particular, the sensing element requires very low propagation loss waveguides which can best be realised from Si3N4 or Ta2O5. The optimised Si3N4 or Ta2O5 waveguides however are not optimal for other functions and this is shown and alternatives explored where the Si3N4 or Ta2O5 can easily be co-integrated. The fabrication process of low loss Si3N4 and Ta2O5 waveguides are also reported in this thesis. Si3N4 films were grown by using low pressure chemical vapor deposition (LPCVD) technique. Dry etching of Si3N4 films have been optimized to produce smooth and vertical sidewalls. Experimental results predicted that the propagation loss of 0.009 dB/cm is achievable by using optimum waveguide dimensions and silica cladding with the relatively standard processes available within the Laser Physics Centre at the Australian National University. A CMOS back end of line compatible method was developed to deposit good quality Ta2O5 films and silica claddings through ion beam sputtering (IBS) method. Plasma etching of Ta2O5 waveguides has been demonstrated by using a gas combination of CHF3/SF6/Ar/O2. Oxygen was introduced into the chamber to produce non-vertical sidewalls, so the waveguides could be cladded without voids with IBS silica. Average propagation losses of 0.17 dB/cm were achieved from Ta2O5 waveguides which appeared after extensive investigation to be limited by the spatial inhomogeneity of the processing. Lastly, a detailed theoretical and experimental analysis was performed to find out the possible causes of the higher average propagation loss in Ta2O5 waveguides, some sections being observed with 0.02 dB/cm or lower losses