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Design and analysis of low bend losses of the air core optical fiber for wavelength selective devices

100%

Palodiya V. , Raghuwanshi S. K.

Optica Applicata

2015

tom Vol. 45, nr 3

341--353

In this paper, the bending loss, modal field diameter and the modal field distribution of the air core optical fiber are investigated. The effect of optical and geometrical parameters on the bending loss, power confinement and modal field diameter are examined in this special fiber. Detailed design parameters and operation principles of the air core optical fiber are discussed. The structure is based on a unique three layered structure of air core optical fiber, having the central air core, germanium silicate ring core, and silica cladding. It has been demonstrated that air core optical fiber has an excellent mode transformation capability. The air core optical fiber is expected to have a versatile application in local area optical communication networks and tunable wavelength selective devices. The main advantages of air core optical fiber are low bend loss and small mode field diameter, which is a prime focus of this paper.

Simulation of two dimensional photonic band gaps

63%

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

International Letters of Chemistry, Physics and Astronomy

2014

tom Vol. 5

58--88

The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circular and hexagonal GaAs rods as well as triangular lattice of circular and hexagonal air holes in GaAs whereas square lattice of square or circular air holes in a dielectric medium ε = 18 gave complete band gaps. The variation of these band gaps with dielectric contrast and filling factor gave the largest gaps for all configurations for a filling fraction around 0.1.The gap maps presented indicated that TM gaps are more favoured by dielectric rods while TE gaps are favoured by air holes. The geometrical gap maps operating at telecommunication wavelength λ = 1.55 m showed that a complete band gap can be achieved for triangular lattice with circular and hexagonal air holes in GaAs and for honeycomb lattice of circular GaAs rods.

Point Defects in GaAs Photonic Crystals

63%

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

International Letters of Chemistry, Physics and Astronomy

2015

tom Vol. 43

91--102

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.