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Design of a highly sensitive photonic crystal refractive index sensor incorporating ring-shaped GaAs cavity

100%

Rahman-Zadeh F. , Danaie M. , Kaatuzian H.

Opto-Electronics Review

2019

tom Vol. 27, No. 4

369--377

Two highly sensitive optical sensor topologies are proposed and simulated in this paper. The proposed structures are optimized to provide better performance characteristics such as sensitivity, detection limit, and quality factor. They are based on two-dimensional photonic crystals consisting of rectangular arrays of GaAs rods in SiO2 substrates. Such lattices have bandgaps for transverse magnetic modes. Two-dimensional finite difference time domain and plane wave expansion methods are used for the simulation and analysis of the refractive index sensors and particle swarm optimization method is used to optimize the structural parameters. The designed structures show a high sensitivity to refractive index variations. They are able to detect refractive indices from 1.33 to 1.5. An excellent figure of merit equal to 737 RIU−1 is observed for the proposed structure and a significant improvement is observed compared to the structures reported in the literature.

Simulation and design of a wideband T-shaped photonic crystal splitter

100%

Foghani S. , Kaatuzian H. , Danaie M.

tom Vol. 40, nr 4

863--872

In this paper, a high efficiency 2-D T-shaped photonic crystal beam splitter is proposed. It consists of a square lattice of GaAs rods (n = 3.4) embedded in air. The photonic crystal structure proposed can be used for 1550 nm wavelength, which is an important wavelength for optical fiber data transmission. Finite difference time domain (FDTD) simulation results demonstrate that a conventional T-junction can only provide 78% transmission coefficient (39% for each branch) for the incident light, while the proposed T-shaped splitter transmits over 90% of the incident light beam (over 45% from each branch) in the single mode region of waveguide. Especially it transmits nearly 98% (49% from each branch) of the input light in the wavelength of 1550 nm. In other words, the proposed devise shows higher beam splitting efficiency and a wider range of flatness of transmission power spectrum in comparison with previous works.

Optimization of two- dimensional photonic crystal waveguides for TE and TM polarizations

100%

Danaie M. , Attari A. R. , Mirsalehi M. M. , Naseh S.

Optica Applicata

2008

tom Vol. 38, nr 4

643-655

In this paper, we optimize the geometries of some 2D photonic crystal waveguides to increase their single-mode bandwidths for TE and TM polarizations. Using the Plane Wave Expansion (PWE) method combined with optimization algorithm, we find the local maxima as well as the global maximum. A photonic crystal waveguide geometry is proposed which has a single-mode normalized bandwidth of 41% for TM polarization. This value is about 7% greater than the corresponding value for the commonly used square lattice of dielectric rods in which a row is removed. Also, some waveguide geometries are proposed for TE polarization and it is shown that one of these geometries can provide a single-mode bandwidth of 39%, while the widest bandwidth reported so far for the TE case is 21%. The dielectric material used for both cases is GaAs with a dielectric constant of 11.4.