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1

Numerical simulations of a simple refractive index sensor based on side-hole optical fibres

Dudek Michał, Köllő Kinga K.

Opto-Electronics Review

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2022

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Vol. 30, No. 4

art. no. e143607

EN

In this work the influence of the cavity parameters on optical losses of a simple intensitybased in-line refractive index sensor utilizing a micromachined side-hole fibre was studied by means of numerical simulations. To perform these simulations, the Authors used the finite-difference time-domain method. The proposed sensor setup consists of light source, micromachined optical fibre as a sensor head, and a detector which makes it low-cost and easy to build. The changes of the external refractive index can be, therefore, recovered by direct measurements of the transmitted intensity from which insertion loss values can be calculated. By changing geometry of the cavity micromachined into the side-hole optical fibre, it was possible to determine its influence on the final sensor sensitivity and measurements range. Based on the provided analysis of simulations results, a simple fibre optic sensor can be fabricated mainly for sensing external liquids refractive index for application in biochemistry or healthcare.

2

Gold nano-elliptic arrays used in plasmonic waveguides in near infrared spectrum

Nurmohammadi T., Yadipour R., Abbasian K.

Optica Applicata

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2018

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Vol. 48, nr 3

489--497

EN

In this paper, we investigated plasmonic waveguides in near infrared spectrum, especially at original (λ = 1310 nm) and also communication bands (λ = 1550 nm) using gold nano-elliptic rings. It is possible to shift localized surface plasmon resonance, by appropriate geometrical properties, to the desired wavelength. Three-dimensional simulations utilizing the finite-difference time-domain algorithm are used to determine the set of geometrical parameters of gold nano-elliptic rings for exciting localized surface plasmon resonance at 1310 and 1550 nm. Employing different configurations of gold nano-elliptic rings chains, waveguides are designed, with–3 dB transmission loss coefficients and group velocities calculations for different modes. In comparison with circular nanorings, elliptic rings showed better characteristics, such as high electric field enhancements and low loss transmission coefficients.

3

Design of a novel photonic crystal 1.31/1.55 µm bi-band filter for near infrared application

Lallam F., Badaoui H., Abri M., Fedaouche A.

Optica Applicata

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2018

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Vol. 48, nr 3

341--348

EN

A novel design of a double selective filter for integrated optics in two-dimensional photonic crystals operating at a wavelength of 1.31 and 1.55 µm is proposed in this paper. We focus particularly on filters transmission and selectivity enhancement. The two-dimensional photonic crystals filters are simulated by using a combination of three cascaded waveguides; these later are conceived by one missing row and with different rods radii for efficient filtering purpose. The properties of these photonic crystal structures are numerically investigated by using the two-dimensional finite-difference time-domain method and the numerical results are given for incident light wave having transverse electrical polarization. A final synthesized filter topology is presented and the maximum of transmission is found around 70% and 60% localized respectively near 1.31 and 1.55 µm wavelengths.

4

A simple model of the scanning near-field optical microscopy probe tip for electric field enhancement

Wang Y., Cai W., Yang M., Liu Z., Shang G.

Optica Applicata

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2017

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Vol. 47, nr 1

119--130

EN

In this paper, we present a simple near-field probe model that is composed of an elongated ellipsoid and a finite metal truncated cone. The elongated ellipsoid has been shown to act as a protrusion or separate particle near a truncated cone apex with strong near-field enhancement under laser excitation. By controllably varying the length of the ellipsoid protrusion from the truncated cone, the truncated cone-ellipsoid probes can be adapted to the suitability of near-field probes. The effects of substrate material and excitation wavelength on the near field enhancement for different tip apexes are also discussed. In addition, we compared the properties of the truncated cone-ellipsoid probe with the widely used hemisphere conical tip by launching surface plasmon polaritons on plasmonic waveguides to prove the suitability of the truncated cone-ellipsoid probes as high performance near-field probes. The present simple model would provide a theoretical basis for the actual construction of probes.

5

Finite-difference time-domain solution of second-order photoacoustic wave equation

Rahimzadeh A., Chen S.-L.

Optica Applicata

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2016

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Vol. 46, nr 3

435--446

EN

A finite-difference time-domain numerical solution is presented for solving a single second-order photoacoustic equation, instead of solving three coupled first-order equations. In this way, we are able to insert the heating function to the simulation directly instead of initial pressure. Results are validated using k-Wave simulation and show a good agreement for future development. The perfectly matched layer boundary condition has been implemented for a second-order photoacoustic equation and results are compared to Dirichlet, Neumann and Mur boundary conditions.

6

Miniaturization of bandstop filter using double spurlines and double stubs

Angkawisittpan N.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 11a

178-181

EN

This paper presents a new type of compact bandstop filter. The proposed filter topology consists of double spurlines and double open stubs. Double spurlines are introduced to a conventional open stub filter for filter circuit size miniaturization and bandstop region improvement. It is clearly shown that the rejection region of the proposed filter is wider and deeper compared to the conventional open stub filter without any cascading circuits or periodic structures. The proposed filter is designed with Finite-Difference Time-Domain Method (FDTD). To validate the proposed topology, a compact filter prototype with bandstop centered at 3.5 GHz is fabricated and transmission coefficient measurements are conducted. Measurements show that there is a rejection region from 1.68 to 5.17 GHz with S21 less than -3 dB. The total length of the prototype equals to 49.2 mm.

PL

W artykule przedstawiono kompaktowy filtr pasmowo-zaporowy, zawierający podwójne struktury mikropaskowe i podwójne pętle otwarte. Przy projektowaniu wykorzystano metodę różnic skończonych w dziedzinie czasu (ang. Finite-Difference Time-Domain Method).

7

Routing properties of the T-structure based on Au/SiO2 nanorings in optical nanophotonic devices

Ahmadivand A.

Optica Applicata

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2012

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Vol. 42, nr 3

659-666

EN

In the present paper, we have utilized Au nanoring arrays in an SiO2 host to provide a T-structure for the purpose of routing and switching optical energy in optical integrated devices to operate at optical communication band (? ? 1550 nm). To employ this router at spectral region considered, localized surface plasmons resonance (LSPR) must be red-shifted around 1550 nm. This T-shaped router includes Au nanorings with a 175 nm inner diameter, a 35 nm thickness and a 35 nm height, and the intercenter distance between two nanorings is 330 nm. To demonstrate the routing properties, we utilized the finite-difference time-domain (FDTD) method. It is shown that the non-straight chain can transport and route the optical energy with certain velocity of light and transmission coefficient. In addition, the percentage of transmitted or power ratio for this structure has been calculated as almost 90%. The optical energy transport can take place at group velocity of approximately 25% of the velocity of light (0.25c0, where c0 is the velocity of light in the vacuum). The router based on nanoring chains shows better performance in switching and transporting the optical energy in comparison to other nanoparticles (nanospheres, nanodisks and nanorods).

8

The Electromagnetic Field Parallel Cluster Simulation on an Anatomic Human Head Model

Walendziuk W., Tarasow E., Idzikowki A.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 3

92-93

EN

In the paper the way of computations of electromagnetic field scattering in a numerical model of human head is demonstrated. The work presents a structure of a model based on the MRI (Magnetic Resonance Image). In the parallel program, which is used in the computations, the FDTD (Finite-Difference Time-Domain) method was implemented. The software was applied in the three-node cluster of workstations (COW).

PL

W niniejszym artykule przedstawiono metodę obliczania propagacji pola elektromagnetycznego w anatomicznym modelu głowy ludzkie. W pracy przedstawiono strukturę badanego modelu opartego na obrazach, otrzymanych metodą rezonansu magnetycznego (MRI). Do obliczeń wykorzystano program równoległy, zaimplementowany w sieci klaster, opartej na trzech węzłach, który opracowano na podstawie metody różnic skończonych w dziedzinie czasu FDTD (Finite-Difference Time-Domain

9

Computation of SAR and Temperature Increase Distribution in Human Body Numerical Model

Walendziuk W., Forenc J.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 3

88-89

EN

The following paper presents the procedure of the SAR (Specific Absorption Rate) determination distribution used by the authors. In order to conduct it, the FDTD (Finite-Difference Time-Domain) method was used. Its parallel version working on a cluster system was implemented. Computations of the SAR coefficient and the temperature increase were based on numerical model of human head consisting of eleven tissues. Conclusions contains the comparison of the achieved results with those of other authors’.

PL

W artykule przedstawiono wykorzystaną przez autorów publikacji procedurę wyznaczania rozkładu SAR (Specific Absorption Rate). W tym celu posłużono się metodą FDTD (Finite-Difference Time-Domain), którą zaimplementowano w wersji równoległej pracującej w sieci komputerów klaster. Przeprowadzone doświadczenia obliczania współczynnika SAR oraz przyrostu temperatury oparto na modelu głowy ludzkiej, zbudowanej z jedenastu tkanek. W podsumowaniu przedstawiono porównanie otrzymanych wyników z badaniami innych autorów.