Gap maps and intrinsic diffraction losses in one-dimensional photonic crystal slabs

A theoretical study of photonic bands for one-dimensional (1D) lattices embedded in planar waveguides with strong refractive index contrast is presented. The approach relies on expanding the electromagnetic field on the basis of guided modes of an effective waveguide, and on treating the coupling to radiative modes by perturbation theory. Photonic mode dispersion, gap maps, and intrinsic diffraction losses of quasi-guided modes are calculated for the case of self-standing membranes as well as for Silicon-on-Insulator structures. Photonic band gaps in a waveguide are found to depend strongly on the core thickness and on polarization, so that the gaps for transverse electric and transverse magnetic modes most often do not overlap. Radiative losses of quasi-guided modes above the light line depend in a nontrivial way on structure parameters, mode index and wavevector. The results of this study may be useful for the design of integrated 1D photonic structures with low radiative losses.Comment: 9 pages, 8 figures, submitted to Physical Review

Modelling of photonic wire Bragg Gratings

Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

Subwavelength silicon photonics: keynote presentation

2020 Photonics North (PN), Niagara Falls, ON, Canada, 26-28 May 2020Subwavelength structures are enabling a host of high-performances devices in the silicon photonic platform. Here we review our progress in the field, with an emphasis on the auspicious anisotropic properties of these structures for applications ranging from broadband on-chip GRIN-lenses, to zero-birefringence waveguides and polarization splitters

Theory and numerical modelling of parity-time symmetric structures in photonics: introduction and grating structures in one dimension

A class of structures based on PT PT-symmetric Bragg gratings in the presence of both gain and loss is studied. The basic concepts and properties of parity and time reversal in one-dimensional structures that possess idealised material properties are given. The impact of realistic material properties on the behaviour of these devices is then investigated. Further extension to include material non-linearity is used to study an innovative all-optical memory device

Fiber optic surface plasmon resonance sensor with a Bragg grating

We report a new optical sensor based on excitation of a surface plasmon (SP) in an optical fiber Bragg grating (FBG) structure. The sensing device consists of a side-polished single-mode optical fiber with a Bragg grating written into a fiber core and a thin gold overlayer supporting SP. If a coupling between a guided mode of the optical fiber and a SP mode is established, any change in the refractive index of analyte affects propagation constant of the fiber mode producing a change in the amount of light reflected by the FBG. A laboratory prototype of the sensor has been developed and its potential for refractometry has been examined. It has been demonstrated that the sensor's sensitivity to refractive index is as high as 750 dB/RIU (Refractive Index Unit)

Advances in development of miniature fiber optic surface plasmon resonance sensors

We present an optical sensor based on excitation of surface plasma waves in optical fiber structure consisting of a sidepolished single-mode polarization-maintaining fiber and a metal overlayer. We describe two modes of operation of the sensor in which variations in the refractive index of the sample are determined by measuring changes in the transmitted optical power at a fixed wavelength (amplitude mode) and by measuring changes in the wavelength at which the resonant attenuation of the fiber mode occurs (spectral mode). We demonstrate that this design allows suppressing sensitivity of the sensor to deformation of the fiber yielding an improved stability and resolution.</p

Separation of refractive index and temperature measurements using surface plasmon-coupled fiber grating

A new fiber optic sensor based on Bragg reflection influenced by a surface plasmon is presented. This arrangement allows for self-referencing due to its highly polarization-resolved response

Neurocognition in schizophrenia: a study of the productivity and visibility of spanish authors

This paper provides a map of the scientific productivity of authors affiliated to a Spanish institution and who have addressed one of the most important current topics in schizophrenia: The study of cognitive performance. A search of the Web of Science yielded 125 articles that met the inclusion criteria. In order to provide a comprehensive overview of scientific productivity, we examine several bibliometric indicators, concerning both productivity and impact or visibility. The analysis also focuses on qualitative aspects of key theoretical importance, such as the kinds of cognitive functions that are most often assessed and the tests most widely used to evaluate them in clinical practice. The study shows that interest in the subject of cognitive function in schizophrenia has increased considerably in Spain since the beginning of this century. The results also highlight the need to standardize the type of tests to be used in the cognitive assessment of patients with schizophrenia