Photonic bandgap materials: design, fabrication, and characterization

The last few decades have seen a tremendous explosion in the area of new synthetic materials. As we begin to better understand the nature of the atomic and molecular bonds it has been possible to systematically search for materials with specific properties thanks to the availability of powerful supercomputers. Due to significant advances in materials synthesis a rich variety of artificial materials whose mechanical, chemical, electronic and optical properties can be suitably tailored can now be produced. Some of the materials (plastics, synthetic fibers, ceramics, alloys etc.) can replace or substitute traditional materials; some others have managed to create new applications themselves (semiconductors, superconductors, optical fibers etc.). Over the last decade there has been a growing interest in a new material called photonic bandgap structures which can manipulate light in an extraordinary way opening up new possibilities in the area of optics and optoelectronics, eventually paving the way for optical computing. Proof of principle structures that demonstrates the expected property has been successfully fabricated for low frequency electromagnetic waves. However, making photonic bandgap structures that can operate at visible frequency is quite challenging. This is because photonic bandgap material are essentially periodic dielectric structures where the periodicity is on the order of the wavelength of light. The goal of this dissertation is to develop a technique for the fabrication inverse FCC photonic crystals that can operate at the visible and near infrared frequencies. The technique essentially focuses on employing self organizing systems such as monodisperse colloidal systems of polystyrene microspheres as a basis for forming periodic structure at submicron dimensions. The main aspects are first to show that the experimental procedure for fabrication developed in this dissertation actually has the desired structural property. Demonstration of structural properties is done by means of optical microscopy and scanning electron microscopy. The other aspect is to demonstrate that the photonic structure so produced indeed shows effects due to photonic bandgap. Optical spectroscopy of the samples is used to show that these samples indeed show the pseudogap that has been theoretically predicted for photonic crystals made with the materials used

Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis

Two possibilities exist for the evolution of individual enzymes/proteins from a milieu of amino acids, one based on preference and selectivity and the other on the basis of random events. Logic is overwhelmingly in favour of the former. By protein data base analysis and experiments, we have provided data to show the manifestation of two types of preferences, namely, the choice of the neighbour and its acceptance from the amino end (left) or the carboxyl end (right). The study tends to show that if the 20 proteinous amino acids were made to combine in water, the resulting profile would be nonrandom. Such selectivity could be a factor in protein evolution

One-step transformation of 2-oxa-3-azabicyclo[2.2.1]hept-5-ene and methyl 2,3-diazabicyclo[2.2.1]heptane-2-carboxylate to ion uptake systems

Linker generated duplexes of the title compounds- prepared from cyclopentadiene- with possibility for positioning of four oxygen in the cavity, are shown to be excellent ion uptake systems. Mass spectrometric doping studies with lithium, sodium, potassium and silver ions, show a clear preference for lithium complexation. The lithium salts of the best examples have been prepared and characterized

Twisted split-ring-resonator photonic metamaterial with huge optical activity

Coupled split-ring-resonator metamaterials have previously been shown to exhibit large coupling effects, which are a prerequisite for obtaining large effective optical activity. By a suitable lateral arrangement of these building blocks, we completely eliminate linear birefringence and obtain pure optical activity and connected circular optical dichroism. Experiments at around 100-THz frequency and corresponding modeling are in good agreement. Rotation angles of about 30 degrees for 205nm sample thickness are derived.Comment: 6 pages, 4 figure

Phonon-polaritonics: enabling powerful capabilities for infrared photonics

Here, we review the progress and most recent advances in phonon-polaritonics, an emerging and growing field that has brought about a range of powerful possibilities for mid- to far-infrared (IR) light. These extraordinary capabilities are enabled by the resonant coupling between the impinging light and the vibrations of the material lattice, known as phonon-polaritons (PhPs). These PhPs yield a characteristic optical response in certain materials, occurring within an IR spectral window known as the reststrahlen band. In particular, these materials transition in the reststrahlen band from a high-refractive-index behavior, to a near-perfect metal behavior, to a plasmonic behavior – typical of metals at optical frequencies. When anisotropic they may also possess unconventional photonic constitutive properties thought of as possible only with metamaterials. The recent surge in two-dimensional (2D) material research has also enabled PhP responses with atomically-thin materials. Such vast and extraordinary photonic responses can be utilized for a plethora of unusual effects for IR light. Examples include sub-diffraction surface wave guiding, artificial magnetism, exotic photonic dispersions, thermal emission enhancement, perfect absorption and enhanced near-field heat transfer. Finally, we discuss the tremendous potential impact of these IR functionalities for the advancement of IR sources and sensors, as well as for thermal management and THz-diagnostic imaging

Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis †

Two possibilities exist for the evolution of individual enzymes/proteins from a milieu of amino acids, one based on preference and selectivity and the other on the basis of random events. Logic is overwhelmingly in favour of the former. By protein data base analysis and experiments, we have provided data to show the manifestation of two types of preferences, namely, the choice of the neighbour and its acceptance from the amino end (left) or the carboxyl end (right). The study tends to show that if the 20 proteinous amino acids were made to combine in water, the resulting profile would be nonrandom. Such selectivity could be a factor in protein evolution. [Ranganathan S, Kundu D and Vudayagiri S D 2003 Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis; J. Biosci. 28 [683][684][685][686][687][688][689][690

Feature issue introduction: Beyond Thin Films: Photonics with Ultrathin and Atomically Thin Materials

Rapid advances in nanotechnology have brought about the realization of material films that may comprise only as little as a few atomic layers. For example, semiconductors and metals of sub-10 nm thicknesses have been realized. Then, the graphene paradigm inspired a plethora of other 2D and quasi-2D materials. In this new era, materials have transcended beyond the traditional thin films to a domain of atomic-scale thicknesses, unleashing vast and unexplored possibilities for light-matter interactions. This Optical Materials Express virtual issue features a collection of thirty-five papers aiming to capture the current state-of-the art, trends and open research directions in photonics with ultrathin and atomically thin materials