Showing papers by "Marian Marciniak published in 2013"

Accurate Analysis of Light Scattering and Absorption by an Infinite Flat Grating of Thin Silver Nanostrips in Free Space Using the Method of Analytical Regularization

Abstract: We study the plane wave scattering and absorption by a flat grating of thin silver nanostrips located in free space, in the visible-light range. The formulation involves generalized boundary conditions imposed on the strip median lines. We use an accurate numerical solution to this problem based on the dual-series equations and the method of analytical regularization. This guarantees fast convergence and controlled accuracy of computations. Reflectance, transmittance, and absorbance as a function of the wavelength and the grating parameters are analyzed. In addition to well-known surface-plasmon resonances, sharp resonances are revealed in the H-polarized scattering near but not equal to the Rayleigh wavelengths of nonzero diffraction orders; in the E-polarized scattering these resonances are not visible. Asymptotic formulas for the frequencies and natural fields of the grating resonances are presented.

Applications of Ground Penetrating Radar in civil engineering — COST action TU1208

Abstract: This paper focuses on the use of Ground Penetrating Radar (GPR) in civil engineering. Open issues in this field are identified and desirable advances in GPR technology, application procedures, data processing algorithms and analysis tools, are addressed. European associations, institutes and consortia interested in this topic are mentioned, together with the main relevant international events. The new COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” is presented, started in April 2013: this interdisciplinary project offers important research opportunities and will strengthen European excellence in all the fields concerning the success of GPR technique, with a main focus on its applications in civil engineering. Four Working Groups (WGs) carry out the research activities: WGI focuses on the design of innovative GPR equipment, on the building of prototypes, as well as on the testing and optimization of new systems; WG2 focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids; WG3 deals with the development of electromagnetic forward and inverse scattering methods and of advanced data processing algorithms; WG4 explores the use of GPR in fields different from civil engineering and the integration of GPR with other nondestructive testing techniques. The COST Action TU1208 is still open to the participation of new parties: in this paper, information is provided for scientists and scientific institutions willing to join the Action and participate to its activities.

Optimizing the structure of optical temperature sensors on the base of slot and double-slot ring waveguides with liquid crystal filling

Abstract: We consider the design methods and operation principles of a fast-response optical sensor for precise measurement of small temperature variations, which is based on ring resonators of micron size made from waveguides with one or two slots filled by a liquid crystal. The sensor sensitivity and measurement region can be changed by modifying the parameters of the waveguide or resonator, such as width of the waveguide strips or slots, slot separation, resonator bend radius, coefficient of coupling between the ring and input/output waveguides, etc. We analyzed the dependence of the transverse field distribution and effective indices of the orthogonally polarized modes in the slot and double-slot waveguides on the waveguide and resonator parameters, and we have considered the optimization of the temperature sensor structure based on such waveguides.

Modeling of a discrete parabolic reflector made of sub-wavelength plasmonic wires

Abstract: Focusing of waves using solid reflectors is widely used in optics and quasioptics, parabolic reflectors being the most popular and efficient ones. Periodically structured scatterers have been attracting attention of researchers for a long time because of the interesting effects of extraordinary large reflection, transmission and near-field enhancement [1-4]. For the finite periodic gratings of metal scatterers this is explained by effects of surface-plasmon (P) resonances, that are observed on sub-wavelength noble-metal particles and wires in the midinfrared and optical bands [5-7], and grating (G) resonances that are induced by the periodicity [3,4,8]. Excitation of plasmons leads to powerful enhancement of scattered and absorbed light. The wavelengths of the P-resonances depend mainly on the object shape and less on its dimensions. The wavelengths of the Gresonances lie near the Rayleigh wavelengths [9] of linear gratings and hence weakly depend on both the elementary wire shape and its dimension, provided that the wire size is a fraction of the period. In the wave scattering by sparse infinite gratings, G-resonances lead to almost total reflection of the incident field in narrow wavelength bands.

Grating resonances on periodic arrays of sub-wavelength wires and strips: Historical narrative and possible applications

Abstract: This paper reviews the history of discovery and the study of the nature of the high-quality natural modes existing on periodic arrays of sub-wavelength scatterers as specific periodically structured open resonators. Here, the arrays can be finite and infinite, and their elements can be dielectric and metallic. These grating modes (G-modes), like any other natural modes, are the “parents” of corresponding resonances in the electromagnetic-wave scattering and absorption. In the scattering cross-sections, they are usually observed as Fano-shape (double-extremum) resonances, while in the absorption they always display conventional Lorentz-shape peaks. Thanks to high tunability, the G-resonances can potentially supplement or even replace the better known surface-plasmon resonances in the design of nanosensors, nanoantennas, and nanosubstrates for surface-enhanced Raman scattering.

High Q-factor Fabry-Perot microresonator as an alternative to microdisk in electro-optical modulator for microwave-photonic receivers

Abstract: In the last decade a new idea has been suggested for receivers of communication systems, namely, in microwave receivers’ architecture. Though superheterodyne radio-frequency receivers are best suited to the needs of contemporary wireless communication, however stray radiation of their local oscillator (heterodyne) interferes with neighboring radio-devices and permits to locate the covert receiver. To overcome this drawback the signal transfer to optical range has been suggested. By this conversion, not only an elimination of receiver’s stray radiation is attained but also vast advantages of photonic signal processing become available. The key element of existing microwave-photonic receivers is electro-optical microdisk modulator. However, its realization is complicated and as an alternative an electro-optical modulator based on high Q-factor Fabry-Perot microresonator is suggested. Comparative analysis of both types of modulators is performed, and advantages of high Q-factor Fabry-Perot microresonator based modulator are highlighted. Keywords—electro-optical modulator, microwave-photonic receivers, wireless communication.

Grating resonances as an alternative to plasmon resonances in nanophotonics applications

Abstract: We present a mini-review on the discovery, nature and characterization of the specific family of natural modes existing on periodic arrays of both dielectric and metallic sub-wavelength scatterers, and the corresponding to them resonances in the optical-range wave scattering and absorption. These grating modes (G-modes) have been studied analytically for the gratings of thin flat strips and those of circular wires. It has been shown that, for infinite gratings, their complex-valued natural frequencies tend to the Rayleigh anomalies if the cross-sectional area of the strip or wire becomes smaller. Therefore their quality factors, in this idealized case, display unlimited growths. For finite-size gratings the G-mode quality factors are finite and controlled by the number of elements. If they are made of noble metals and their number is in hundreds, the G-modes have much higher quality factors than the better-known surface-plasmon modes. Therefore the former have potential to replace the latter in the design of sensors in applications related to the detection of changes in the refractive index of the host medium.

Analysis of orthogonally polarized modes in curved slot and double-slot waveguides

Abstract: We analyze the dependence of transverse field distribution and effective indices of the two orthogonally polarized modes in slot and double-slot waveguides on waveguide parameters (slot width, slot separation) and bend. Optimization of the parameters of microring resonator on the base of such waveguides used as a temperature sensor is considered.

Periodicity assisted scattering and absorption of light by finite layered gratings of silver nanowires

Abstract: We consider the two-dimensional (2-D) problem of the H-polarized plane wave scattering by discrete arrays made of finite number of periodically arranged circular cylindrical nanowires. Using the Fourier expansions of the field in local coordinates and addition theorems for cylindrical functions, we perform analytical regularization and obtain a block-type matrix equation. This equation is cast to the Fredholm second-kind form that guarantees, after truncation, the convergence of numerical solution. In computations, we consider the gratings with shifted layers made of silver nanowires in the visible-light range of wavelengths. The scattering and absorption cross-sections and near-field patterns are calculated and the interplay of plasmon and periodicity-induced resonances is studied.

Optimization of gyrotropic double-periodic perforated layer for Brewster's angle polarizer design

Abstract: We develop the analytical solution to the problem concerning the plane wave scattering from a double-periodic gyrotropic layer in quasi-static case, i.e. if the structure periods are much smaller than the wavelength and the field remains approximately constant over the period. Using the solution [1], obtained by the Method of Integral Functionals based on the rigorous integral-differential equations [2] we drived the analytical expressions for the scattered fields in the single-mode approximation, i.e. by retaining only the zero diffraction orders in the full-wave Floquet expansions.

Enhanced temperature sensing with liquid-crystal filling

Abstract: The wide use of automated control and actuation systems, the adoption of new technological processes, and conversion to flexible manufacturing systems have stimulated the development of sensing and measurement devices. Sensors are also important elements of fire-alarm and disaster-protection systems. As well as high metrological (measurement) performance, sensors must offer reliability, durability, stability, light weight, compact size, low power consumption, and compatibility with microelectronic information processing devices. Fiber and integrated optical devices are those best able to fulfill all these requirements.1 Waveguide devices, in particular, have the capability to measure small changes in refractive index, and hence the physical quantities that cause those changes. An interesting design for sensing purposes is the slot waveguide, which consists of two strips of a high-refractive-index material separated by a subwavelength-scale region of lowrefractive-index material (the slot). The electric field discontinuity that arises at the interface between high-index-contrast materials results in high optical intensity concentration in the low-index slot region.2 This ability of a slot waveguide to strongly confine light, combined with the properties of a microring resonator (an optical waveguide in a closed loop having micron-scale radius), has shown great potential for optical sensing applications. As an improvement on this design, waveguides with a double-slot arrangement have also been proposed in recent years. Micro-ring resonators based on such double-slot waveguides have been shown to tolerate larger fabrication errors than their single-slot counterparts.3 Moreover, sensitivity can be enhanced by filling the waveguide slot with a substance whose refractive index is responsive to the parameter being measured. In the case of temperature sensing, we have found liquid crystal (LC) to be a useful and interesting filling material Figure 1. Structure of a double-slot waveguide micro-ring resonator showing the waveguide mode transverse electric field distribution (black curve). Liquid crystal (LC) fills the ring waveguide slots.

Role of periodicity in the scattering by a cloud of randomly located plasmonic nanowires

Abstract: We consider the problem of the H-polarized plane wave scattering by a linear chain of silver nanowires in a cloud of similar arbitrarily located wires, in the visible range. Numerical solution uses the field expansions in local coordinates and addition theorems for cylindrical functions and has a guaranteed convergence. The total scattering cross-sections and near-zone and far-zone field patterns are presented. The observed resonance effects are studied and compared with their counterparts in the scattering by the same linear chain of wires in free space.