N. Kejalakshmy

Soft Glass Equiangular Spiral Photonic Crystal Fiber for Supercontinuum Generation

An equiangular spiral photonic crystal fiber (ES-PCF) design in soft glass is presented that has high nonlinearity ( gamma > 5250 W-1 middot km-1 at 1064 nm and gamma > 2150 W-1 middot km-1 at 1550 nm) with a low and flat dispersion (D ~ 0.8 ps/kmmiddotnm and dispersion slope ~ -0.7 ps/km middot nm2 at 1060 nm). The design inspired by nature is characterized by a full-vectorial finite element method. The ES-PCF presented improves over the mode confinement of triangular core designs and dispersion control of conventional hexagonal PCF, combining the advantages of both designs; it can be an excellent candidate for generating supercontinuum pumped at 1.06 mum.

Design and Characterization of Low-Loss Porous-Core Photonic Crystal Fiber

A rigorous modal solution approach, based on the numerically efficient finite-element method (FEM), has been used to design and characterize a photonic crystal fiber (PCF) with a porous air core, which has the potential for use for low-loss guidance of terahertz (THz) waves. Here, for the first time, it is reported that a large fraction of the power that is also well confined in the waveguide can be guided in the low-loss air holes, thus to reduce the overall modal loss. This novel PCF design can readily be fabricated by use of a range of techniques including stack-and-draw, extrusion, and drilling.

Golden spiral photonic crystal fiber : polarization and dispersion properties

A golden spiral photonic crystal fiber (GS-PCF) design is presented in which air holes are arranged in a spiral pattern governed by the golden ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The birefringence and polarization properties of this fiber are analyzed using a vectorial finite-element method. The fiber that is investigated shows a large modal birefringence peak value of 0.016 at an operating wavelength of 1.55 microm and exhibits highly tuneable dispersion with multiple zero dispersion wavelengths and also large normal dispersion. The GS-PCF design has identical circular air holes that potentially simplify fabrication. In light of its properties, the GS-PCF could have application as a highly birefringent fiber and in nonlinear optics, and moreover the 2D chiral nature of the pattern could yield exotic properties.

Characterization of silicon nanowire by use of full-vectorial finite element method

We have carried out a rigorous H-field-based full-vectorial modal analysis and used it to characterize, more accurately, the abrupt dielectric discontinuity of a high index contrast optical waveguide. The full-vectorial H and E fields and the Poynting vector profiles are described in detail. It has been shown through this work that the mode profile of a circular silicon nanowire is not circular and also contains a strong axial field component. The single-mode operation, vector field profiles, modal hybridness, modal ellipticity, and group velocity dispersion of this silicon nanowire are also presented.

Ultra low bending loss equiangular spiral photonic crystal fibers in the terahertz regime

An Equiangular Spiral Photonic Crystal Fiber (ES-PCF) design in Topas® for use in the Terahertz regime is presented. The design shows ultra low bending loss and very low confinement loss compared to conventional Hexagonal PCF (H-PCF). The ES-PCF has excellent modal confinement properties, together with several parameters to allow the optimization of the performance over a range of important characteristics. A full vector Finite Element simulation has been used to characterize the design which can be fabricated by a range of techniques including extrusion and drilling.

Rigorous modal analysis of silicon strip nanoscale waveguides.

A full-vectorial H-field Finite Element Method has been used for the rigorous modal analysis of silicon strip waveguides. The spatial variation of the full-vectorial H and E-fields are also discussed in details and further, the Poynting vector is also presented. The modal area, hybridness, single mode operation and birefringence are also described for such silicon strip waveguides.

Rigorous characterization of acoustic-optical interactions in silicon slot waveguides by full-vectorial finite element method

For the first time detailed interactions between optical and acoustic modes in a silicon slot waveguide are presented. A new computer code has been developed by using a full-vectorial formulation to study the acoustic modes in optical waveguides. The results have shown that the acoustic modes in an optical slot waveguide are not purely longitudinal or transverse but fully hybrid in nature. The model allows the effects of Stimulated Brillouin Scattering and the associated frequency shift due to the interaction of these hybrid acoustic modes with the fully hybrid optical mode also to be presented.

Metal-Coated Defect-Core Photonic Crystal Fiber for THz Propagation

Modal solutions for metal-coated defect-core photonic crystal fiber (PCF) with a central air-hole have been obtained by using a full-vectorial finite element method to model the guidance of THz waves. It has been shown that the surface plasmon modes can couple with the defect-core PCF mode to form supermodes, with potential for sensing applications.

Mode degeneration in bent photonic crystal fiber study by using the finite element method

The development of highly dispersive lower and higher order cladding modes and their degeneration with respect to the fundamental core mode in a bent photonic crystal fiber is rigorously studied by use of the full-vectorial finite element method. It is shown that changes in the bending radius can modify the modal properties of large-area photonic crystal fibers, important for a number of potential practical applications.

Numerical Analysis of Second Harmonic Generation in Soft Glass Equiangular Spiral Photonic Crystal Fibers

In this paper, the accurate and numerically efficient finite element (FE)-based beam propagation method (BPM) has been employed to investigate second harmonic generation (SHG) in highly nonlinear soft glass (SF57) equiangular spiral photonic crystal fibers (ES-PCFs) for the first time. It is shown here that the SHG output power in highly nonlinear SF57 soft glass PCF exploiting the ES design is significantly higher compared with that of silica PCF with hexagonal air-hole arrangements. The effects of fabrication tolerances on the coherence length and the modal properties of ES-PCF are also illustrated. Moreover, phase matching between the fundamental and the second harmonic modes is discussed through the use of the quasi-phase matching technique. Furthermore, the ultralow bending loss in the SF57 ES-PCF design has been successfully analyzed.