Symmetry in photonic crystals is reflected in the structure of their photonic bands and symmetry breaking can result in the development of complete photonic band gaps, leading to enhanced optical properties. This can be difficult for self-assembled nanostructures, due to their restriction by fundamental principles to preferential geometries, but can be achieved through the application of external stimuli. In order to explore such an approach, elastomeric, nanoengineered, polymer photonic crystal structures have been fabricated on a large scale, through a method of shear induced self-assembly of 200nm monodisperse, polymer spheres with a core-shell structure. Determination of the assembly geometry through light diffraction experiments reveals a highly symmetric structure of close-packed, core-shell particles, with its orientation governed by the directionality imposed by the fabrication procedure. In these tuneable photonic crystals, application of external strain at directions of different crystallographic symmetry, accompanied by synchronised optomechanical measurements, reveals strong anisotropic optomechanical properties. It is shown that mechanical properties are primarily dominated by the viscoelastic nature of the shell material, while the strain-induced symmetry breaking reveals previously forbidden resonant peaks. Experiments involving uniaxial extension at principal and non-principal directions verify the underlying symmetry of the crystal lattice and consistently reproduce the anisotropic optical properties, providing information regarding the dual microstructure that controls the optomechanical response of these systems. Simulations based on a model of close-packed hard spheres predict the appearance of secondary resonances and suggest a structural transition from an fcc to a lower symmetry monoclinic crystal lattice. A more elaborate micromechanical model does not verify this transition but predicts the strain dependence of dominant spectroscopic peaks. Experiments involving different crosslinking densities reveal individual contributions from the elements comprising the material's dual microstructure. The inherently low refractive index contrast featured by these polymeric systems forbids the development of full photonic band gaps but symmetry based principles can be applicable to other structures with similar topological restrictions. Results provide a possible route for fabrication of active deformable nanostructures and aid our understanding of self-assembly in these complex systems, leading to optimised large-scale fabrication.

No description available.

In recent years, nanoprobe-based devices have attracted significant attention and found a wide range of applications, including nanostructure imaging, single molecular detection, and physical, chemical, and biological sensing applications. However, since the scale of nanodevices is substantially less than the optical diffraction limit, their fabrication remains a difficult challenge. Despite significant efforts, most of the fabrication techniques developed so far require expensive equipment and complicated processing procedures, which has hindered their applications. In this thesis, we developed a new class of fluorescent nanoprobes consist of a silica fiber taper, a single carbon nanotube, and nanoscale fluorescent elements (such as semiconductor quantum dots). This nanoprobe provides a natural interface between the nanoscale structures (i.e., the fluorescent elements) and the microscale structure (i.e., the fiber taper), which can significantly simplify their fabrication. Furthermore, since the nanoscale fluorescent elements are produced through bottom-up processes such as chemical synthesis, we can easily tailor the functionalities of such fluorescent nanoprobes to many different applications in nanophotonics, including near field imaging, nonlinear optics mapping, and quantum electrodynamics. We have custom designed an optical system for this nanoprobe fabrication. We have characterized the nanoprobes using transmission electron microscope (TEM) and scanning electron microscope (SEM) and performed preliminary experiments on near field scanning. Our current fabrication/imaging systems can be readily upgraded to achieve more advanced applications in nonlinear optics and quantum optics. / Master of Science

表面電漿是由貴金屬表面電荷密度漲落引起的沿著金屬表面傳播的電磁波。在過去十年裡，表面電漿效應因其在光子器件，傳感，表面增強螢光，尤其是表面增強拉曼散射(SERS) 方面的應用而引起了廣泛的關注.許多著作中的結論已經證實了的預期的SERS 強度，因此使得基於各種不同納米結構中的熱點的SERS變成一種下一代超敏感生物傳感平臺。因為表面電漿的波長和材料介電性質密切相闕，受f於此，難以進一步減小，所以對於進一步的各種應用來說，保證產生高強度的表面電漿使至關重要。同時，用電漿實現納米光子器件已經引起了研完者長久的興趣。例如，基於等問距規則排列的密置金屬納米顆粒之間突破衍射極限的的近場耕合已經被用於傳輸光信號。但是，輻射和吸收損耗在此類波導中是很嚴重的。因此，設計新概念的電漿器件是急需的。 / 有鑒於上述種種問題，本論文集中于總結構和材料兩方面剪裁表面電漿以期達到下面的要點和目的: / (1)基於傳播電漿(PSPs) ，或者傳播電漿同局域電漿(LPRs) 的結合而發展新的簡單的器件，由此提供顯著的聚焦、電磁場和場強增強。這種器件可以應用於很多方面，包括依賴強場的生物分子傳感探測，以及非線性光學效應。 / (2) 設計基於增益介臂的低損耗的納米光子學器件，這種器件能夠為納米光子器件提供切實的可行性。針對表面電漿共振和電漿結構植于的介電環境之間聯繫，獲得其理論闡釋。這一工作將可以為傳感和器件設計提供深入的理解。 / 本論文中我們已經得到了如下的成果: / (1)一種基於將表面電漿聚焦到金屬盤中心孔而實現級聯放大增強的SERS 激勵源被提出和理論研究。這種器件提供了準均勻，水平偏振，較大面積的強SERS 激勵源。如時域有限差分(FDTD) 方法所揭試，強度譜線和波長範圍在650-1000 nm的近場性質展混出了一系列增強模式。在最佳的增強模式下，孔洞中的電場可以使得SERS 信號獲得四次方的進一步增強。同時一種解析模型也被提出來給FDTD結果以精確的解釋。我們的模型同時揭示了通過侵化金屬盤尺度而得到八次方場增強的可能性。我們的結果表明極強的電場增強，並且聚焦的電場是平行于金屬盤平面的效果，只能在中間包含一個孔洞的中空金屬盤(HMDs) 中才可能實現。這是因為金屬盤中間絶悸的問時的存在使得孔洞邊棒的電子不能流通間隙，進進而使得高強度的電場可以存在。另一方面，在實心的金屬盤的情形下，電子流會傾向於抑制到達中心的表面電漿的強度。除了產生高度優化的SERS 熱點，這種大面積的活性孔洞在螢光增強和非線性光學中也提供了一些潛在的應用。 / 除了中空金屬盤，基於經由增孟輔助下PSPs 的LPRs 之間的衍射共掠，我們開發了另一種一種高度侵化的熱點。由此得到的器件被理論上分析。衍射共振的過程是經由下述過程實現的:由LPRs 實現的光場局域化， LPRs 和PSPs 相互作用，以及通過PSPs 的能量傳遞。我們的研究表明通過給PSPs 引入光學增孟，可以從一種激光過程中的到LPRs 非常強的電磁場增強。我們發現通過現實的增豆豆水平，局域電場的增強引子可以達到10⁷。因此，我們為實現依賴強電場的單分子SERS提供了一種理想的方案，並且這種方案也是一種納米激光的新機制。 / (2) 基於增孟輔助的電漿共振金屬納米顆粒鏈，我們提出了一種低損耗納米尺度的波導。我們證明通過引入增孟材料或者引入適當的介電材料作為周圍環境，波導的損耗可以顯著減小。為了得到低損耗傳翰的復介電譜，我們開發了一種高效的膺正交基展開(POBE) 方法。本徵模式分析揭示了低損耗模式的物理源頭，同時給出了除了基於單體偶極共振傳輸之外能量傳輸的可能性。我們提出一種基於電子書刻蝕和化學合成納米顆粒的一種製備方案。這種電漿波導可以構成納米光學器件的基石，尤其是用於集成納米光子學線路。同時，我們原創的揭示表面電漿的物理機理的POBE 方法可以用於進一步研究優化增豆豆輔助的電漿結構，進而設計良好的納米光子器件。 / 本論文始於一個古老問題:宏觀尺度下基於傳統介電材料光聚焦和傳導，并最後終結於納米尺度內經由增益材料和電漿結構的表面電漿的聚焦、和引導。論文結尾，本文給出了展望以及幾種可能的器件實現方案。 / Surface plasmons (SPs) are electromagnetic waves that propagate along the surface of a noble metal via fluctuations in electron density. In the last decade, SPs effects gained widespread attention for their potential application in photonic devices, sensing, surface-enhanced fluorescence, especially Surface-Enhanced Raman Scattering (SERS). Many published results have confirmed the expected strengths of SERS, hence making it possible for SERS to become a next generation ultra-sensitive biosensing platform, which may take the form of various nano-structures in order to achieve optimized hot spots. While the wavelength of SPs is closely related to material dielectric properties and has limited scope for further reduction, it is of critical importance to ensure that SPs are being generated with the highest intensity before any further application advancement is possible. Meanwhile, plasmonics has aroused longstanding interests among researchers to realize nanophotonic devices. For example, ordered arrays of closely spaced metallic nanoparticles (MNP) have been employed to transport optical signals via near-field coupling below the diffraction limit. However, radiation and absorption losses in these waveguides can be serious. New concepts for novel plasmonic devices are essential. / In light of these issues, this thesis focuses on tailoring SPs from the viewpoints of structural and material properties with the following objectives: / (1) To develop a new class of simple plasmonic devices based on tailoring of propagating surface plasmons (PSPs) or cooperation between PSPs and localized plasmon resonance (LPRs) to offer significant field focusing and intensity enhancement. It can serve a wide range of applications, including high field related biomolecular sensing and detection as well as non-linear optical effects. / (2) To design low loss nanophotonic wave guides based on gain medium, which may offer real opportunity for practical nanophotonic devices. To obtain a theoretical interpretation of relationship between surface plasmon resonance and host environment where the plasmonic structure embedded. This study should provide further insight towards sensing and device design. / We have achieved the following results in this project: / (1) A novel SERS excitation source based on focusing of surface plasmons around the center hole of a metal disk for cascaded enhancement is put forward and studied theoretically. The device offers intense SERS excitation with quasi-uniformity and horizontal polarization over a comparatively large hole. As revealed by fmite-difference time-domain (FDTD) method, the intensity spectra and the characteristics of the near field for the wavelength range of 650-1 000 nm exhibit a number of enhancement modes. Electric field intensity of the optimal mode enhances the SERS signal inside the hole by over four orders. An analytical model was also developed to gain precise interpretation on FDTD results. Our model also reveals the possibility of achieving eight orders of enhancement by optimizing the scale of the disk. Our results indicate that much higher electric field enhancement in hollow metal disks (HMDs) can only be possible when we have a hole at the centre and the direction of the focusing field is parallel to the surface of the plasmonic device. This is because of the presence of an insulating gap at the center, that higher level of electric field can exist as electrons are not allowed to flow pass the gap. On the other hand, in the case of a solid metal disk, the flow of mobile electron will tend to dampen the amplitude of the arriving SPs. In addition to generation of highly optimized hot spots for SERS, the large active hole also offers potential applications in fluorescence enhancement and nonlinear spectroscopy. / In addition to HMDs, we also develop a kind of highly optimized hot spots based on diffraction coupling between LPRs via gain-assisted PSPs. Thus derived device was theoretically analyzed. The process of diffraction coupling is achieved via localization of light by LPRs, LPRs-PSPs interplay and PSPs transfer. Our study shows that by incorporating optical gain to PSPs, a very strong boost of the electromagnetic enhancement of LPRs can be expected from a lasing process. We find that with a practical gain level, the enhancement factor of local electric field intensity can be larger than 10⁷. Hence, we offer an ideal configuration to realize high-field dependent single molecule SERS and also a newly applied physical scheme for nano-Iaser. / (2) We propose a low-loss nanoscale wave guide based on gain-assisted plasmonic resonance MNP chain. We demonstrate that by employing a gain material or even an appropriate dielectric for the host environment, waveguide loss can be reduced dramatically. A highly efficient pseudo-orthonormal basis expansion (POBE) method for obtaining the complex dielectric spectra of the low-loss transmission has been developed. Eigenmode analysis revealed the physical origin of those low-loss wave guiding modes, which opens the possibility to achieve waveguiding other than using conventional dipolar resonances of individual particles. A scheme based on electron beam lithography and chemically synthesized nanoparticles has been proposed to fabricate the device. Such plasmonic waveguides may serve as building blocks for making nanoscale optical devices especially for integrated nanophotonic circuits. Meanwhile, the originally developed POBE method, which reveals the general physical mechanism of SPs, can be used to further explore optimized gain-assisted plasmonic structures to design favorable nanophotonic devices. / This thesis begins with an old problem: light focusing and guiding in macroscopic scale with traditional dielectric, and sum up finally with SPs focusing and guiding in nanoscale with gain material and plasmonic material. An outlook is presented at last with several potential schemes for the device realization. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Haixi. / "September 2011." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 124-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter Chapter1 --- Introduction --- p.1 / Chapter 1.1 --- Towards field intensity focusing and guiding of electromagnetic wave --- p.1 / Chapter 1.2 --- Surface plasmons as a route to realize electromagnetic field focusing and waveguiding in nanoscale --- p.3 / Chapter 1.3 --- Structure of this thesis --- p.10 / Chapter Chapter2 --- Plasmonic near field engineering: structural and material aspects --- p.13 / Chapter 2.1 --- Light focusing using near field oflocalized plasmon resonances --- p.13 / Chapter 2.2 --- Plasmonic near field focusing through propagating surface plasmons --- p.30 / Chapter 2.3 --- Various schemes for near field focusing through surface plasmons --- p.33 / Chapter 2.4 --- Guiding surface plasmons in nanoscale --- p.35 / Chapter 2.5 --- Gain-assisted surface plasmons: a different path to field enhancement and guiding --- p.38 / Chapter Chapter3 --- Surface plasmons: characteristics and methodology --- p.42 / Chapter 3.1 --- Characteristics of localized plasmon resonance --- p.42 / Chapter 3.2 --- Localized plasmon resonance: Mie theory and its variations --- p.44 / Chapter 3.3 --- Characteristics of propagating surface plasmons --- p.49 / Chapter 3.4 --- Reflection Pole Method for studying propagating surface plasmons in multilayer structures --- p.55 / Chapter 3.5 --- Pseudo-orthonormal basis expansion method: a new mathematical scheme for modeling surface plasmons --- p.58 / Chapter Chapter4 --- High field generation through intensity focusing of propagating surface plasmons --- p.62 / Chapter 4.1 --- Introduction --- p.62 / Chapter 4.2 --- The hollow metal disk design and its characteristics --- p.64 / Chapter 4.3 --- Quasi-uniform excitation source based on focusing of propagating surface plasmons for cascade enhancement of surface enhanced Raman scattering --- p.68 / Chapter 4.4 --- Conclusions and outlook --- p.78 / Chapter Chapter5 --- High field generation through intensity enhancement of localized plasmon resonance from gain-assisted diffraction coupling --- p.81 / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Diffraction excitation of localized plasmon resonance from propagating surface plasmons --- p.83 / Chapter 5.3 --- Diffraction coupling of localized plasmon resonance through gain-assisted propagating surface plasmons --- p.89 / Chapter Chapter6 --- Gain-assisted plasmonic waveguides based on nanoparticle chains: an effective device approach for achieving low loss in nanoscale dimensions --- p.97 / Chapter 6.1 --- Introduction --- p.97 / Chapter 6.2 --- Theoretical study of near-field particle interactions in active plasmon wave guides --- p.99 / Chapter 6.3 --- Routing and splitting of electromagnetic energy in nanosphere plasmon waveguides --- p.103 / Chapter 6.4 --- Conclusions --- p.107 / Chapter Chapter7 --- Conclusions and outlook --- p.109 / Appendix --- p.117 / Bibliography --- p.124

Metasurfaces, a new class of artificial media attracting great research interest, are composed of a two-dimensional ensemble of designer optical antennas arranged with subwavelength separation that introduce spatially-varying optical properties (e.g., amplitude, phase and polarization). By engineering the subwavelength optical antennas and integrating with functional materials, metasurfaces can manipulate light at one’s will and have led to the demonstration of many exotic electromagnetic phenomena. Metasurfaces have the potential to replace bulky optical components and devices as they are ultra-thin (subwavelength thickness), light weight, and able to provide new functionalities and overcome the limitations of their conventional counterparts. There are a number of promising areas in fundamental research and practical applications where metasurfaces could have a significant impact. In this dissertation, I studied the fundamental physics of the strong interaction between light and metasurfaces and explored passive and active nanophotonic devices based on metasurfaces. I demonstrated metasurface-based devices showing record-breaking or completely novel functionalities; these devices include optical modulators for dynamic control of light propagating in free space over an unprecedented broad wavelength range, photonic integrated devices with record-small footprints, and metasurface sensors orders of magnitude more sensitive than the state-of-art sensing techniques. Strongly correlated perovskites possess widely tunable electronic structure that can host a variety of phases. Nickelates, in particular, undergo electric-field-tunable phase transitions with dramatic changes in the optical properties. In Chapter 2, I will describe my discovery of a new optical phase-transition material SmNiO3 and experimental demonstration of strong optical modulation utilizing the large and non-volatile optical refractive index change associated with electron-doping induced phase transition of SmNiO3. Large electrical modulation of light over a broad wavelength range, from the visible to the mid-infrared,  = 0.4 m – 17 m, is demonstrated using thin-film SmNiO3. By integrating SmNiO3 and plasmonic metasurface structures, modulation of a narrow band of light that resonantly interacts with the metasurfaces is realized. Furthermore, solid-state electro-optic modulators are demonstrated by integrating SmNiO3 and solid polymer electrolytes. Correlated perovskites with tunable and non-volatile electronic phases create a new platform for active photonic devices, such as optoelectronic modulators, electrically programmable optical memories, smart windows, and variable emissivity coatings. Research on metasurfaces has so far focused on controlling wavefronts of light propagating in free space, and the implication of metasurfaces on integrated photonics has not been explored. I conducted initial work on using metasurfaces to control light propagation on a chip. In chapter 3, I will show that gradient metasurface structures consisting of phased arrays of plasmonic or dielectric nano-antennas provide a platform to control guided waves via strong optical scattering at subwavelength intervals. Such gradient metasurfaces enable the creation of small-footprint, broadband, and low-loss photonic integrated devices. I will describe experimental demonstration of waveguide mode converters, polarization rotators, and asymmetric optical power transmission in waveguides patterned with plasmonic gradient metasurfaces. I will also describe experimental demonstration of all-dielectric on-chip polarization rotators that are based on phased arrays of Mie resonators and have negligible insertion losses. Metasurfaces emerge as a new promising photonic platform for biosensing because they offer strong optical confinement and tunable optical resonances. In chapter 4, I will show that metasurface-based biosensors consisting of gold nano-antenna arrays loaded with graphene and working in the mid-infrared spectral range can achieve simultaneous high-sensitivity and high-specificity detection of biomolecules. The biosensors support a hybrid plasmon-phonon resonant mode that concentrates incident light into deeply subwavelength optical spots with local light intensity enhancement by a factor of 104. Strong light-molecule interactions in these optical spots allow for determing protein molecule concentrations via spectral shifts of the plasmon-phonon resonance. A combination of passive and active tuning of the metasurface sensors allows for spectrally overlapping the plasmon-phonon resonance and the vibrational modes of protein molecules, so that I can identify protein molecules via their characteristic mid-infrared “fingerprints”. The high sensitivity and specificity of the metasurface sensors enable the detection of the secondary structure of protein immunoglobulin (IgG) molecules with a sensitivity four orders of magnitude higher than that of conventional attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR).

No description available.

In this thesis numerical methods are used to understand the individual and collective optical response of metal nanoparticles (MNPs). In particular, finite 1D assemblies of MNPs are characterized by analytical solutions to Maxwell's equations. Small particle solutions such as the well-established plasmon hybridization scheme as well as a novel circuit model explaining the intrinsic mechanisms of free electron dynamics help to characterize the optical response of single and coupled MNPs. Complex systems of closely spaced MNPs with small interparticle gaps are studied with the help of full scattering solutions to Maxwell's equations. It is shown that higher order plasmon modes facilitate strong near-fields between MNPs, and in linear chains foster specific optical attributes which are present in more complex systems, playing a key role in energy propagation along practical MNP waveguides.

Due to the massive computational power, Graphics Processing Units (GPUs) have become a popular platform for executing general purpose parallel applications. The majority of on-chip communications in GPU architecture occur between memory controllers and compute cores, thus memory controllers become hot spots and bottle neck when conventional mesh interconnection networks are used. Leveraging this observation, we reduce the network latency and improve throughput by providing a nanophotonic ring network which connects all memory controllers. This new interconnection network employs a new routing algorithm that combines Dimension Ordered Routing (DOR) and nanophotonic ring algorithms. By exploring this new topology, we can achieve to reduce interconnection network latency by 17% on average (up to 32%) and improve IPC by 5% on average (up to 11.5%). We also analyze application characteristics of six CUDA benchmarks on the GPGPU-Sim simulator to obtain better perspective for designing high performance GPU interconnection network.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, April 2010.