Broad spectral tunability is a desired feature of many photonic and plasmonic components, such as optical filters, semiconductor lasers, and plasmonic materials. Here I show that unique properties of long-range surface plasmon polaritons (LR SPP) allow one to produce optical components with very wide tuning range using small variations in the refractive index of the dielectric cladding material. As a proof-of-concept demonstration, I present operation of LR-SPP-based bandpass optical filters in which a 0.004 variation in the refractive index of the cladding dielectric translates into 210 nm of bandpass tuning at telecom wavelengths. The tuning mechanism proposed here may be used to create monolithic bandpass filters with tuning range spanning over more than an optical octave, compact and widely-tunable diode and quantum cascade laser systems, multi-spectral imagers, and other plasmonic components with broadly-tunable optical response. / text

Optical molecular imaging has burgeoned into a major field within biomedicine, and technologies that incorporate surface plasmon resonance effects have become a major focus within this field. Plasmon resonance has been defined as the collective oscillation of the conduction band electrons in certain metals (such as gold) in response to an electric field, such as an impinging wave of light. We show that elastic light scattering due to the plasmon resonance of nanometer-sized gold particles makes them powerful tools for optical imaging of epidermal growth factor receptor (EGFR) expression -- a major biomarker for carcinogenesis. Optical technologies in general are poised as cheap, flexible ways to aid in diagnosis and treatment of disease. In addition to supplying a bright, stable optical scattering signal and a convenient conjugation platform for targeting molecules, these materials display a unique behavior termed "plasmon coupling". This term refers to the dramatic optical property changes brought about by the presence of other nearby nanoparticles. These changes include a dramatic red-shifting in their peak plasmon resonance wavelength, as well as a non-linear, per-particle increase in the overall scattered power. We show that such conditions exist in cells and are primarily due to intricate protein trafficking mechanisms as part of the EGFR life-cycle. The observed variations in plasmon coupling can give clues as to the nanoscale organization of these important proteins. In addition, the resulting optical property changes result in a large, molecular-specific contrast enhancement due to the shifting of the resonance closer to the near infrared region, where biological tissues tend to be most transparent. Despite this enhancement, however, many tissues contain large endogenous signals, as well as barriers to delivery of both light and the nanoparticles. As such, we also show an example of a multifaceted approach for further increasing the apparent molecular-specific optical signals in imaging of EGFR expression by using an oscillating magnetic field. This serves to encode the signal from magnetically susceptible plasmonic nanoparticles, making their extraction from the background possible. Overall, the studies presented in this dissertation should serve to stimulate further investigations into a wide variety of technologies, techniques, and applications.

Patterned arrays of metallic nanostructures are commonly used in photonics, electronics, as well as functional materials and biotechnology because of their unique electronic and optical properties. Although great effort has been devoted to the development of nano-patterning techniques in the past decades, there are still existing challenges for nano-fabrication to achieve fine resolution and complex features over macroscopic areas in a reasonable time period. Herein, we devise two versatile patterning strategies, namely indentation colloidal lithography (ICL) and oblique colloidal lithography (OCL), for the stepwise patterning of planar substrates with numerous complex and unique designs. Those strategies combine colloidal self-assembly, imprint molding in conjunction with capillary force lithography and reactive ion etching, all of which are simple and straightforward. Hexagonal arrays of symmetric and nonconcentric gold features are fabricated on glass substrates with highly controllable geometric parameters. The width, size and asymmetry of each surface structure could be tuned down to the ~10 nm level while the scale of the patterned area could exceed 1 cm^(2). Moreover, our technique also leads to the ability to develop an enormous variety of patterns through stepwise amplification of feature types. In particular, some of the features are fabricated for the first time, including target-triangle, hexagram, hexagram-dot and triangle-dot. Distinctive surface plasmon resonance (SPR) properties, such as higher order surface plasmon modes and Fano resonances are both observed from our patterns, which would be highly desired forthe study of plasmonic coupling. In addition, we have demonstrated a surface orientation dependent Raman selectivity on two nano-structures for the first time. Molecular vibrations with opposite symmetries can be selectively enhanced on different substrates. As a demonstration, this property is applied to the odd-even effect of n-alkanethiol self-assembly monolayers (SAMs) on the gold surface. The alternative alternation of the intensity ratios of two vibration pairs have been shown by surface enhanced Raman spectroscopy (SERS) as a function of the number of carbon atoms. The results obtained exhibit high sensitivity and excellent agreement with previous publications.

Surface plasmon is a collective oscillation behavior of electrons in metal nanoparticle induced by the excitation of incident light, which can create an enhanced localized electric field near the surface of metal nanoparticle. To date, metal nanoparticle surface plasmon resonances have been extensively studied in the photoluminescence domain; little work however was devoted to electroluminescent and photovoltaic research. In this thesis, as a fundamental study we firstly investigated surface plasmon enhanced europium complex luminescence and obtained an improved understanding of the importance of optical spacer in metal enhanced fluorescence phenomenon. Under this guideline, we incorporated metal NPs into organic light emitting diodes (OLED) and organic solar cells, by means of thermal evaporation and wet chemistry. Metal nanoparticles are demonstrated to enhance the efficiency of both OLEDs and solar cells only under tailored device architecture. The surface plasmon enhanced local electric field plays an important and comprehensive role in enhancing device performance. In Alq3 based OLED we observed increased charge carrier injection by depositing Ag nanoparticles underneath the Al cathode; in Ir(ppy)3 based OLED we gained enhanced luminous efficiency via doping silica functionalized Ag nanoparticles into emitting layer; in P3HT based organic polymer solar cell we noticed an increased polymer absorption by incorporating Ag nanoparticles over the active layer. On the other hand, adverse effects such as metal nanoparticle induced charge carrier recombination and light extinction are also observed. The study of surface plasmon effects in organic optoelectronic devices reveals interesting surface plasmon features and permits to optimize optoelectronic devices from a novel point of view. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-01-05 17:22:40.074

A novel surface plasmon resonance sensor is fabricated to evaluate its use in biochemical sensing. The sensor can differentiate between bulk refractive index changes and surface binding reactions of interest. There has been a great interest in developing sensors to differentiate biological or chemical agents from interfering effects, but they still remain in research phase. In this work, a prism coupler is used to simultaneously excite both long and short range surface plasmon modes of the sensor. The differing sensitivities of the long and short range modes allow one to distinguish surface binding reactions of interest from refractive index fluctuations. In this thesis, we have demonstrated the sensors self referencing capability by detecting the formation of an octadecanethiol self assembled monolayer while varying solution refractive index.

Integrated optics present a potentially low cost and higher performance alternative to electronics in optical communication systems. Surface plasmon waveguides (SPWGs) offer a new approach for manipulating light in integrated optical chips. SPWGs provide several advantages over dielectric waveguides. In this study, a fabrication process for SPWGs is developed. SPWGs are fabricated with various lengths and bend radii to allow for study of absorption and bending losses in the waveguides at telecommunications wavelengths (~1550nm). Finite-element method models of straight, bent, and optically coupled waveguides are developed and analyzed.

This thesis report works on optically characterizing waveguide based biosensors consisting of thin, narrow Au stripes embedded in CYTOP. The devices were examined using an ever evolving and improving interrogation setup, variations of which are described in detail in this document. A number of changes were made to the setup configuration in order to reduce noise levels and increase efficiency and accuracy of acquired measurements. Waveguides of varying configurations (straight waveguides and Mach-Zehnder Interferometers with etched and cladded channels) are described and optically characterized. The characterization results of these devices are presented in this thesis. Bulk index measurements are carried out in order to determine a suitable bio-sensing solution with a refractive index matched to that of CYTOP. Step index measurements clearly distinguishing the introduction of sensing solutions of refractive indices varying from one another, are made available. Preliminary bio-sensing experiments involving detection of change in refractive index of sensing fluid as well as adlayer thickness with the introduction of analytes binding to the waveguide surface that has been functionalized with antibodies, using both straight and cladded waveguides with single mode outputs are studied.

As the developments in nanoscale fabrication and characterization technology, the investigation and applications of light in metal nanostructures have been becoming one of the most focused research areas. Metal materials allow to couple the incident light energy into electromagnetic waves propagating on the metal surface under certain configurations, which is called surface plasmon (SP). This feature tremendously expanded the application possibility of metals in optical regime, such as extraordinary transmission (EOT), near-field optics and surface enhanced spectroscopies. In this talk, various metal structures will be demonstrated which could control SP’s propagation, resonance andlocal field enhancement. A number of SP applications are benefited – the plasmonic bragg reflector (PBR), the frequency sensitive plasmonic microcavity, the subwavelength metallic taper, the long range surface plasmon (LRSP) waveguide and surface enhanced Raman spectroscopy (SERS). Especially for SERS, long-term effort was devoted into it to achieve the single molecule detection limit. / Graduate

Heat shock protein 70 (HSP70) is an important health related biomarker, being implicated as an early stage cancer marker and as an indicator of cardiac health. It also has important implications in wildlife environmental monitoring, as its levels can be affected by food deprivation, elevated temperatures, and pollution. Therefore, the use of HSP70 as a biomarker is highly desirable, yet the current methods of quantifying HSP70 are time consuming, expensive, and require dedicated labs. In order to facilitate widespread use of the HSP70 biomarker, a quantification tool that can be used at the point-of-care is needed. This implies the development of a simple and inexpensive HSP70 biosensing technique that is highly sensitive and selective. Therefore, in this work a label-free HSP70 biosensor has been designed based on the optical properties of gold nanoparticles (NPs). Gold NPs exhibit a large absorbance peak in the visible spectrum due to localized surface plasmon resonance (LSPR). The peak position is dependent on the local refractive index, which can be employed as a biosensor by selectively capturing the target analyte to the NP surface. To design an LSPR HSP70 sensor, optical and fluidic simulations were developed to determine optimal NP geometries and microchannel dimensions. The results showed optimal response when using 100nmx5nm gold nanotriangles inside of a 100μmx100μm microchannel. Simulations of the sensor performance showed HSP70 detection from 0.92-4000ng/ml with a resolution of 1.1ng/ml, all of which satisfied the design requirements. An LSPR sensor was experimentally tested at the benchtop scale to prove the concept. Gold NPs were fabricated by electron beam lithography and enclosed in a polymer flow cell. For initial testing of the LSPR sensor, the NPs were functionalized with biotin for selective capture of streptavidin. Streptavidin was detected in real time over the range 55-500,000ng/ml. The use of bovine serum albumin (BSA) was shown to be necessary to block non-specific binding sites to ensure a streptavidin-specific response. The LSPR sensor was then demonstrated to detect salmon HSP70 at 4600ng/ml using its synthetic antibody. Overall, these results demonstrate that LSPR can be used to realize an HSP70 biosensor suitable for point-of-care applications.

The study and applications of surface plasmon polaritons (SP) – also known as plasmonics – has attracted the interest of a wide range of researchers in various fields such as biology, physics, and engineering. Unfortunately, the large propagation losses of the SP severely limit the usefulness of plasmonics for many practical applications. In this dissertation a new wave guiding mechanism is proposed in order to address the large propagation losses of the plasmonic guides. Possible applications of this guiding scheme are also investigated. The proposed hybrid plasmonic waveguide (HPWG) consists of a metal layer separated from a high index slab by a low index spacer. A detailed analysis is carried out to clarify the wave guiding mechanism and it is established that the mode guided by the HPWG results from the coupling of a SP mode and a dielectric waveguide mode. A two dimensional HPWG is proposed and the effects of various parameters on the HPWG performance are analyzed in detail. This structure offers the possibility of integrating plasmonic devices on a silicon platform. The proposed waveguide supports two different modes: a hybrid TM mode and a conventional TE mode. The hybrid TM mode is concentrated in the low index layer, whereas the conventional TE mode is concentrated in the high index region. This polarization diversity is used to design a TM- and a TE-pass polarizer and a polarization independent coupler on a silicon-on-insulator (SOI) platform. Moreover, the performance of a HPWG bend is investigated and is compared with plasmonic waveguide bends. The proposed devices are very compact and outperform previously reported designs. The application of HPWG for biosensing is also explored. By utilizing the polarization diversity, the HPWG biosensor can overcome some of the limitations of plasmonic sensors. For example, unlike plasmonic sensors, the HPWG biosensor can remove the interfering bulk and surface effects.