Resonance and scattering in microstructured optical fibers

We present an investigation into the mechanism for guidance of microstructured optical fibers consisting of high-refractive-index cylinders embedded in a low-index background. A new guidance regime is identified in which the fibers' confinement losses depend strongly on wavelength and the positions of the loss minima and maxima depend on the scattering properties of individual cylinders and only weakly on their position and number. We point out similarities between these results and those reported recently for two-dimensional antiresonant reflecting waveguides.     

Fiber-based tunable dispersion compensation

Tunable dispersion has been implemented in various technology platforms, including fiber gratings, planar waveguides, thin film etalons, and bulk optic technologies. This paper will focus on fiber grating based tunable dispersion compensation, because fiber gratings are at present one of the best developed TDC technologies available. The paper is divided into three parts. In the first part we describe grating based TDC technologies and discuss their advantages and disadvantages. We focus on thermally tuned linearly chirped fiber gratings, as these have to date been the most successful grating technology for 40 Gbit/s. We also compare grating TDCs to two other prominent tunable dispersion technologies: thin film etalons and planar waveguide ring resonators. In the second section we describe the techniques used to fabricate high performance dispersion compensation gratings as well as the theory of the primary defect of fiber grating dispersion compensation: group delay ripple (GDR). In the third section we describe the telecom system related issues for tunable gratings, including characterization of grating performance, tunability requirements and results from actual system trials using tunable FBGs.     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Solitary waves in a nonlinear oppositely directed coupler

The propagation of pulses in the system of two tunnel-coupled optical waveguides from optically nonlinear materials one of which has a negative refractive index, while the other one, positive, is investigated theoretically. The propagation of nonlinear waves in this structure is studied based on the model of coupled modes. For linear waves, this pair of coupled waveguides behaves as a mirror resulting in the change of direction of the energy flow upon penetration of radiation from one waveguide to the other. The solutions to the system of nonlinear equations describing the stationary propagation of the solitary wave, the gap soliton, in a particular direction are found. This soliton is formed by the coupled pair of wave packets each localized in the corresponding waveguide.     

Antiresonant guiding microstructured optical fibers for sensing applications

A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.     

Antiresonant guiding photonic crystal fibers for distributed temperature gradient measurements

We propose, design, and experimentally demonstrate a novel, simple, distributed refractometric measurement technique based on unique spectral properties of antiresonant-guiding photonic crystal fibers for measuring temperature gradients. We use a simple and accurate analytical model and numerical simulations to guide our experiments. The proposed technique may find applications for monitoring and control of chemical and biological reactions in microfluidic systems.     

Metamaterials: electromagnetic enhancement at zero-index transition

Resonant enhancement of electromagnetic waves propagating at oblique incidence in metamaterials, with dielectric permittivity and magnetic permeability linearly changing from positive to negative values, has been predicted and theoretically studied. This effect occurs for both TE and TM polarizations near the point where a refractive index changes its sign. Our model elucidates the unique features of the resonant enhancement in "positive-to-negative transition" metamaterials for a broad frequency range from microwaves to optics.     

Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.     

Antiresonant reflecting photonic crystal optical waveguides

We propose a simple analytical theory for low-index core photonic bandgap optical waveguides based on an antiresonant reflecting guidance mechanism. We identify a new regime of guidance in which the spectral properties of these structures are largely determined by the thickness of the high-index layers and the refractive-index contrast and are not particularly sensitive to the period of the cladding layers. The attenuation properties are controlled by the number of high/low-index cladding layers. Numerical simulations with the beam propagation method confirm the predictions of the analytical model. We discuss the implications of the results for photonic bandgap fibers.     

Optical bistability in a nonlinear optical coupler with a negative index channel

We discuss a novel kind of nonlinear coupler with one channel filled with a negative index metamaterial. The opposite directionality of the phase velocity and the energy flow in the negative index metamaterial channel facilitates an effective feedback mechanism that leads to optical bistability and gap soliton formation.