Conventional passive metamaterials always suffer from the limitation of loss and dispersion due to fundamental causality issue. Especially it becomes severe due to material loss at terahertz frequency. Our work resolves the loss problem by introducing gain device into the metamaterial structure. A passive volumetric metamaterial is firstly designed on the quartz substrate. A negative resistance is inserted into the wire of the structure to provide the gain. We have identified resonant tunneling diodes that work up into THz frequency and shown in simulation that simultaneous negative index and gain can be obtained.

We examine three case studies during the Deep Convective Clouds and Chemistry (DC3) field experiment when storm inflow and outflow air were sampled for aerosol subsaturated hygroscopicity and the real part of refractive index (n) with a Differential Aerosol Sizing and Hygroscopicity Probe (DASH-SP) on the NASA DC-8. Relative to inflow aerosol particles, outflow particles were more hygroscopic (by 0.03 based on the estimated parameter) in one of the three storms examined. Two of three control flights with no storm convection reveal higher values, albeit by only 0.02, at high altitude (> 8km) versus < 4km. Entrainment modeling shows that measured values in the outflow of the three storm flights are higher than predicted values (by 0.03-0.11) based on knowledge of values from the inflow and clear air adjacent to the storms. This suggests that other process(es) contributed to hygroscopicity enhancements such as secondary aerosol formation via aqueous-phase chemistry. Values of n were higher in the outflow of two of the three storm flights, reaching as high as 1.54. More statistically significant differences were observed in control flights (no storms) where n decreased from 1.50-1.52 (< 4km) to 1.49-1.50 (> 8km). Chemical data show that enhanced hygroscopicity was coincident with lower organic mass fractions, higher sulfate mass fractions, and higher O:C ratios of organic aerosol. Refractive index did not correlate as well with available chemical data. Deep convection is shown to alter aerosol radiative properties, which has implications for aerosol effects on climate.

by Woo Ka Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 61-63). / Abstract --- p.i / Acknowledgment --- p.ii / Contents --- p.iii / Abbreviations --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter 1 --- Introduction --- p.1 / Chapter 2. --- Theoretical background / Chapter 2.1 --- Static light scattering for homopolymer --- p.5 / Chapter 2.2 --- Static light scattering for copolymer --- p.16 / Chapter 2.3 --- Dynamic light scattering --- p.19 / Chapter 2.4 --- Modified method for copolymer --- p.28 / Chapter 3. --- Experimental / Chapter 3.1 --- Preparation of PET-PCL --- p.31 / Chapter 3.2 --- Preparation of solution for LLS --- p.31 / Chapter 3.3 --- Refractive index increment measurement --- p.32 / Chapter 3.4 --- Laser light scattering instrumentation --- p.35 / Chapter 4. --- Results and Discussion --- p.36 / Chapter 5. --- Conclusion --- p.60 / Chapter 6. --- References --- p.61

In our modern society, we are surrounded by numerous sensors, constantly feeding us information about our physical environment. From small, wearable sensors that monitor our physiological status to large satellites orbiting around the earth, detecting global changes. Although, the performance of these sensors have been significantly improved during the last decades there is still a demand for faster and more reliable sensing systems with improved sensitivity and selectivity. The rapid progress in nanofabrication techniques has made a profound impact for the development of small, novel sensors that enables miniaturization and integration. A specific area where nanostructures are especially attractive is biochemical sensing, where the exceptional properties of nanomaterials can be utilized in order to detect and analyze biomolecular interactions.  The focus of this thesis is to investigate plasmonic nanoparticles composed of gold or silver and optimize their performance as signal transducers in optical biosensors. Metal nanoparticles exhibit unique optical properties due to excitation of localized surface plasmons, which makes them highly sensitive probes for detecting small, local changes in their surrounding environment, for instance the binding of a biomolecule to the nanoparticle surface. This is the basic principle behind nanoplasmonic sensing based on refractometric detection, a sensing scheme that offers real-time and label-free detection of molecular interactions.  This thesis shows that the sensitivity for detecting local refractive index changes is highly dependent on the geometry of the metal nanoparticles, their interaction with neighboring particles and their chemical composition and functionalization. An increased knowledge about how these parameters affects the sensitivity is essential when developing nanoplasmonic sensing devices with high performance based on metal nanoparticles.

L' ATP es una molecula clau en el metabolisme cel.lular, actuant com a donador d'energia lliure i acoplant reaccions endergoniques i exergoniques. L'ATP es sintetitzat a la mitocondria en un proces anomenat fosforil.lacio oxidativa despres d'una serie de reaccions a la cadena de citocroms que es troba en la membrana interna de l'organel.la. La font d'energia necessaria per aquesta sintesi s'obte en les cel.lules animals dels nutrients de l'ingestio, i de la llum solar en les plantes. Existeix una via alternativa de sintesi d'ATP extramitocondrial, la glicolisi, que s'inicia amb la fosforilacio de la glucosa per l'enzim hexokinasa.Interaccio llum-materiaL'energia electromagnetica l'ona de la qual oscil.la en una longitud d'ona de nanometres es anomenada llum. En aquestes frequencies, l'energia promou excitacio electronica de certs atoms i molecules. Existeix una interaccio diferent de la llum amb molecules, produida per el camp electromagnetic que per definicio la llum provoca en qualsevol medi. El camp electric resultant desplaca els electrons dels enllacos quimics produint una polaritzacio del medi sense que existeixi absorcio de l'energia. Aquest es un mecanisme interactiu que existeix sempre, i es l'unic que es dona en molecules que son transparents (no absorbeixen) per a una determinada frequencia de la llum, com es el cas de l'ATP per l'energia visible i infravermella propera. Experiments, resultats i discussioQuan l'ATP es excitat amb fotons ultraviolats, es produiex una fluorescencia en longituts d'ona visibles. L'io magnesi s'ha utilitzat per estudiar com la llum visible i infravermella propera produiex un desplacament de carregues electriques a la molecula d'ATP. La construccio d'un interferometre de Michelson ha servit per observar l'interaccio no absortiva de la llum i l'ATP. La mesura directa de l'index de refraccio d'una solucio d'ATP dona informacio sobre les caracteristiques electriques del medi. L'observacio de que aquest index canvia despres d'irradiar la solucio amb longituds d'ona visibles i infravermelles properes, confirmen que la llum provoca canvis electrics significatius en l'ATP. En aquest treball tambe s'ha estudiat el comportament bioquimic de l'ATP irradiat quant forma part de dues reaccions quimiques diferents: la de la luciferina-luciferasa i la de la hexoquinasa. En tots dos casos, l'us d'aquest ATP irradiat ha produit una alteracio dels parametres cinetics estudiats, V0 i k en la reaccio de la luciferina-luciferasa, i km i vmax en la reaccio de l'hexoquinasa.ConclusionsAquesta interaccio no absortiva de la llum amb l'ATP es la primera descrita per a una biomolecula. El mecanisme aporta noves dades per explicar els efectes observats en el metabolisme cel.lular despres de l'irradiacio d'organismes, teixits i cultius cel.lulars amb llum visible i infravermella propera. / ATP is a key molecule in cellular metabolism. In this thesis, I examined the effects of visible (635 and 655 nm) and near-infrared (810 and 830 nm) light on ATP in solution. I also examined were the biochemical behavior of light-exposed ATP in the luciferine-luciferase reaction and hexokinase reaction, the initial step in glycolysis that begins extra mithocondrial ATP synthesis. Irradiated groups in the luciferine-luciferase reaction showed an improvement in the kinetic parameters V0 and k, and more ATP molecules reacted with the enzyme when they were excited by light. When irradiated ATP was added to the hexokinase reaction, the experimental groups showed significant differences in the Michaelis-Menten kinetic parameters (km for ATP and vmax) and the rate of product synthesis was greater. Changes in both reactions were wavelength and dose dependant. When ATP was excited with UV photons, it fluoresced. This fluorescence decreased when Mg2+ was added, probably because the ion binds the phosphates, which are the part of the molecule responsible for light emission. Irradiating the ATP-Mg2+ solution with 655 nm and 830 nm light increased the fluorescence resulting from a displacement of charges in the phosphor-oxygen bond that repels Mg2+. The refraction of light in an ATP solution was observed by the Michelson interferometer and by directly measuring the refractive index. The refractive index changed after red and near-infrared light interaction due to a change in the electrical permittivity of the medium. Since ATP in water is transparent to visible and near-infrared light, and is therefore not a chromophore for those wavelengths, I conclude that the observed light interaction with ATP is not due to photon absorption but to the electromagnetic disturbance produced by the light, which leads to a polarization of the dielectric molecule that is ATP. This interaction of visible and near-infrared electromagnetic energy with ATP offers new perspectives for explaining light interaction at subcellular level.

Today's microwave circuits, whether for communication, radar, or testing systems, need compact tunable microwave filters. Since different microwave circuit applications have radically different size, power, insertion loss, rejection, vibration, and thermal requirements, new filter technologies with different balances between these requirements are always desirable. Negative Refractive Index (NRI) transmission media was discovered 10 years ago with the unique property of negative phase propagation. A literature review was conducted to identify potential NRI methods for filters and other devices, but no NRI tunable filters were found. To address this gap, a family of tunable NRI bandpass filters was simulated and constructed successfully using end-coupled zeroth order resonators. Tuning was accomplished by controlling the negative phase length of the NRI sections with varactors. The resulting L-band filters exhibited a 25-40 percent tunable range, no higher order resonances, and required only one fourth the length of a coupled-line filter constructed from traditional 180 degree microstrip resonators.

The resonant absorption, emission, and scattering of light are the fundamental optical processes that have been used both to probe matter and to manipulate light itself. In the last decade there has been essential progress in coherent control of both linear and nonlinear optical responses based on resonant excitation of atomic coherence in multilevel quantum systems. Some interesting and useful phenomena, resulting from coherent control of absorption and the group index, such as electromagnetically induced transparency, lasing without inversion, and ultra-slow group velocity of light have been widely studied. This work is focused on coherent control of refractive index and resonant fluorescence in multilevel medium. We suggest two promising schemes for resonant enhancement of the refractive index with eliminated absorption and propose their implementation in transition element doped crystals with excited state absorption and in a cell of Rb atoms at natural abundance. We show how to use one of these schemes for spatial variation of the refractive index via its periodic resonant increase/decrease, remarkably keeping at the same time zero absorption/gain. It opens the way to production of transparent photonic structures (such as distributed Bragg reflectors, holey fibers, or photonic crystals) in a homogeneous resonant atomic media such as dielectrics with homogeneously distributed impurities, atomic, or molecular gases. These optically produced photonic structures could easily be controlled (including switching on/off, changing amplitude and period of modulation) and would be highly selective in frequency, naturally limited by the width of the optical resonance. We also derive the optical fluorescence spectra of a three-level medium driven by two coherent fields at the adjacent transitions in a general case when all three transitions are allowed. We show that coherent driving can efficiently control the distribution of intensities between the fluorescent channels. In particular, the total intensity of fluorescence at the transition which is not driven by the optical fields may essentially exceed the fluorescence intensity at the driven transitions under the condition of two-photon resonance. This counter-intuitive effect is due to depletion of the intermediate state via atomic interference.

Silicon oxynitride (SiON) films for applications of optical waveguide devices deposited using plasma-enhanced chemical vapor deposition were investigated. The SiON films were deposited on 4¡¨ silicon wafers based on the reaction of N2O/SiH4 precursors. The refractive indices of the films were adjusted by varying the partial pressure of SiH4 in the precursors. In addition, films prepared at conventional flow (~1500 sccm) and low flow (~1000 sccm) conditions were compared. We found that the nitrogen content of the films grown at low flow conditions can be significantly reduced resulting in a reduction of absorption around 1500 nm. Therefore SiON films grown at low flow conditions would be more suitable for optical waveguide fabrication. Finally, with the aid of the beam propagation method (BPM) software, a single-mode optical waveguide based on the proposed technology was designed and fabricated. The propagation loss was 0.79dB/cm for TE polarization, and 0.73db/cm for T

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 126-136). Also available in print.

Academisch proefschrift--Amsterdam. / "Summary": p. 141-142. "Stellingen": [2] p. inserted. "Literatuur": p. 143-145.