Wyniki wyszukiwania - BazTech

1

Narrow transmission mode in one-dimensional symmetric defective photonic crystal containing metamaterial and high Tc superconductor

Srivastava Sanjeev K., Aghajamali Alireza

Optica Applicata

|

2019

|

Vol. 49, nr 1

37--50

EN

We theoretically investigate the properties of narrow transmission mode (defect mode) within the reflection band in one-dimensional symmetric defective photonic crystal containing double negative metamaterial and high temperature superconductors. The transmittance spectrum of the proposed structure is obtained by using the characteristic or transfer matrix method. The results show that by increasing the thickness of air defect, transmission mode shifts towards the lower frequency side. But when the thickness of a superconductor layer is increased, transmission mode shifts towards the high frequency side. Further, the effect of temperature variation of superconducting defect on the defect mode has been investigated and found that when the temperature of superconducting layer increases the frequency of defect mode is red shifted. The shift in frequency has smaller value in the lower temperature region than in the higher temperature region, even if the change in temperature is same. Finally we have discussed the effect of variation of thickness on the defect mode by using the double negative metamaterial as defect layer in place of superconductor layer. The result shows that we get two modes for smaller thickness of double negative layer but only a single mode for larger thickness.

2

Defect modes properties in one-dimensional photonic crystals employing a superconducting nanocomposite material

Aly A. H., Elsayed H. A., Malek C.

Optica Applicata

|

2018

|

Vol. 48, nr 1

53--64

EN

In the present work, we investigate theoretically the transmission characteristics of one-dimensional photonic crystals that contain a defect layer of a nanocomposite material in infrared radiation. The theoretical treatment is obtained depending on the fundamentals of the characteristic matrix method. Here, the nanocomposite designed from nanoparticles of a superconducting material is arranged into a dielectric medium. The numerical results clarify the acute effect of the volume fraction and the operating temperature on the effective permittivity of the nanocomposite material. Therefore, the volume fraction, the operating temperature and other parameters such as the permittivity of the dielectric material and the threshold frequency could have a significant effect on the characteristics of the defect modes. Thus, our structure may be very promising in many applications such as narrow band filters and among optoelectronic applications.

3

Performance study of a liquid-core Bragg fiber sensor in presence of a defect layer

Chourasia R. K., Prasad S., Singh V.

Opto-Electronics Review

|

2017

|

Vol. 25, No. 3

215--221

EN

Performance parameter of a Bragg fiber waveguide based resonant sensor in presence of a defect layer in cladding regions is theoretically studied. The Bragg fiber waveguide consists of a liquid-core surrounded by alternate high and low refractive indices materials in cladding regions. Reflectivity of the proposed waveguide based resonant sensor is formulated using transfer matrix method for a non-homogeneous multilayer cylindrical system. The waveguide shows a band gap region with a narrow defect mode in the band gap region under the considered wavelength range. Instead of taking a whole band gap as a sensing signal, here the defect peak is taken as the sensing signal. It is observed that the intensity of defect mode is more sensitive for core refractive index than the intensity of traditional band gap region (lobe). This study shows that the higher sensitivity can be achieved by creating the defect at a position in cladding region where the intensity of transmitted light lies between 40% and 90%. Presence of a defect layer is able to increase the detection accuracy of the sensor and, hence increase the overall performance of this sensor.

4

Point Defects in GaAs Photonic Crystals

Dissanayake S. E., Wijewardena Gamalath K. A. I. L.

International Letters of Chemistry, Physics and Astronomy

|

2015

|

Vol. 43

91--102

EN

Applying plane wave expansion method to one dimensional multilayer system formed from alternating layers of GaAs and air, a defect mode was artificially introduced by removing a GaAs layer at the centre of a supercell and the band structures and mode field distributions were obtained. The defect mode normalized frequency was 0.28. The parameters for developing a Febry-Perot filter in the visible frequencies are given. The point defects in a two dimensional square lattice formed from GaAs rods of radius 0.16a in air was created by removing one GaAs rod at the centre of a supercell and also by increasing the centre GaAs rod radius to 0.5a. The removal of the rod folded the band structure 25 times creating a localized evanescent defect mode. The increment of the centre GaAs rod radius led to five defect bands inside the band gap with one degenerate state creating a monopole, two quadrupoles and two hexapoles. Evolution of the defect modes with the variation of the radius of GaAs rod is also presented.