We present results for a broadband supercontinuum spanning almost two octaves (575 nm - 1600 nm) generated in
an equiangular spiral photonic crystal fiber proposed earlier. The pump source is taken to be Yb - doped fiber laser at 1.06
μm. The fiber has two zero dispersion wavelength (at 885 nm and 1115 nm) with very high nonlinearity ( >5580 W<sup>-1</sup> km<sup>-1</sup> at 1060 nm).
When the cross-section of an optical waveguide is much smaller than the operating wavelength, unique materials and
structural dependent properties can be observed. In this regard silicon has been particularly attractive as the low-cost and
mature CMOS fabrication technology widely used in the electronics industry can be exploited. The high index contrast
of silicon allows light confinement in submicron size waveguides, along with the creation of very compact bends, to
allow increased functionality of photonic integrated circuits. A rigorously H-field based vectorial modal analysis has
been carried out, which can more accurately characterize the abrupt dielectric discontinuity of a high index contrast
optical waveguide. As a result, the full-vectorial H and E-field and the Poynting vector profiles are shown in detail. The
work done and reported reveals that the mode profile of a circular silicon nanowire is not circular and also has a strong
axial field component. Arising from the results of the analysis, the characteristics of single mode operation, the vector
field profiles, the modal ellipticity and the group velocity dispersion of this silicon nanowire both circular and planar are
presented. The modal hybridness and birefringence of rectangular silicon nanowires and slot-type waveguides are also
A modal solution approach based on a rigorous full vectorial finite element method has been used to determine single
mode single polarization properties of a bent highly birefringent fiber photonic crystal fiber. A design approach for the
single mode single polarization design has been discussed.
Modal solutions for Photonic Crystal with circular and square shaped rods have been obtained using the Finite
Element method. We compare the field distributions and effective indices with rod shape in the Photonic
Crystal. We optimize sharp 90° bends with different rod shape using a Finite Element Time Domain method.
A modal solution approach, based on a powerful, full-vectorial, H-field based finite element method (FEM), has been
used to analyze the single mode operation of a PCF and the modal solution of the fundamental space filling mode has
been analyzed. The FEM with perfectly matched layer condition has been used to characterize the leakage loss of a PCF
and the differential loss between the polarized modes of a PCF and as a result, the design of a single mode single
polarization PCF has also been proposed.
Modal properties of silica waveguides are presented along with their results on single mode operation, spot-size variations, confinement factor and, modal field profiles for different index contrast value between the core and the claddings. Both dominat and non-dominat field profiles and their transverse variations are also shown. Numerically simulated results also suggests that by using the MM-based design a very compact optical power splitter, of the order of 500 μm in length, can be designed, which is much shorter than conventional directional coupler or Y-junction-based designs.
A new method for solving the wave equation is presented, which, being non-paraxial, is applicable to wide-angle beam propagation. It shows very good stability characteristics in the sense that relatively larger step-sizes can be used. It is both faster and easier to implement. The method is based on symmetrized splitting of operators, one representing the propagation through a uniform medium and the other, the effect of the refractive index variation of the guiding structure. The method can be implemented in the FD-BPM, FFT-BPM and collocation schemes. The method is stable for a step size of 1 micron in a graded index waveguide with accuracy better than 0.001 in the field overlap integral for 1000-micron propagation. At a tilt angle of 50°, the method shows an error less than 0.001 with 0.25-micron step. In the benchmark test, the present method shows a relative power of ~0.96 in a 100 micron long waveguide with 1000 propagation steps and 800 sample points, while FD-BPM with Pade(2,2) approximation gives a relative power of 0.95 with 1000 sample points and 2048 propagation steps. Thus, the method requires fewer points, is easier to implement, faster, more accurate and highly stable.
In numerical wave propagation methods, the perfectly matched layer (PML) boundary condition is employed to prevent spurious reflections. However, PML takes additional resources in number of computation points and time. In this study, the PML performance is examined with change in the distribution of sampling points and PML absorption profile with a view to optimizing its efficiency. We have used the collocation method in our examples. We have found that equally spaced field sampling points give better absorption of beams under both optimal as well as non-optimal conditions for lower PML widths. While at higher PML widths, unequally spaced basis points may be more advantageous. The behavior of different absorption profiles varies with point spacing. For numerical tests, Gaussian beam propagation in a homogeneous medium is considered. Comparing different profiles, we find that a new profile sin<sup><i>p</i></sup> with <i>p</i>=4 and quartic profiles are best in equally spaced points, sin<sup>2</sup> and square profiles are best in unequally spaced points.