Kaisar R. Khan

Singular solitons in optical metamaterials by ansatz method and simplest equation approach

This paper derives singular 1-soliton solution for optical metamaterials. There are two integration approaches that obtains the solution. These are the ansatz approach and the simplest equation approach. The second method also leads to an additional set of solutions that emerge as a by-product. These are topological soliton, rational solution and singular periodic solution. The constraint conditions for the existence of these solutions are also exhibited. The numerical simulation of a topological 1-soliton solution is also exhibited.

Optical solitons in nonlinear directional couplers with spatio-temporal dispersion

This paper addresses solitons in nonlinear directional couplers in non-Kerr law media, with spatio-temporal dispersion. Both twin-core couplers as well as multiple-core couplers are studied. The nonlinearities studied are Kerr law, power law, parabolic law, dual-power law and log law. Bright, dark and singular soliton solutions of the governing equation are studied.

OPTICAL SOLITON PERTURBATION IN NANOFIBERS WITH IMPROVED NONLINEAR SCHRÖDINGER'S EQUATION BY SEMI-INVERSE VARIATIONAL PRINCIPLE

This paper studies the perturbation of the improved version of the nonlinear Schrodingers equation that governs the propagation of solitons through nonlinear optical fibers. The semi-inverse variational principle is employed in order to obtain an analytical soliton solution in presence of the perturbation terms. There are three types of nonlinearity that will be studied. They are Kerr law, power law and the log law. The constraint conditions will naturally fall out in order for the soliton solutions to exist. The numerical simulations supplement the analytical results for each of the three laws of nonlinearity.

Raman solitons in nanoscale optical waveguides, with metamaterials, having polynomial law non-linearity

This paper reports bright Raman soliton solutions in optical metamaterials. The polynomial law and triple law non-linearity are discussed. Travelling wave hypothesis is employed to conduct the mathematical analysis. Implicit solutions in terms of elliptic integral of the third kind are obtained. The analytical results are supplemented with numerical simulations.

Optical Gaussons in nonlinear directional couplers

Abstract This paper studies optical Gaussons in nonlinear directional couplers. Both twin-core couplers as well as multiple-core couplers are considered. For multiple-core couplers, coupling with nearest neighbors as well as coupling with all neighbors are considered. A closed form optical Gausson solution is obtained in all of these cases where the amplitude of the Gaussons is governed by a nonlinear difference equation. The domain restrictions naturally fall out as constraint conditions in order for the Gaussons to exist.

Coherent Super Continuum Generation in Photonic Crystal Fibers at Visible and Near Infrared Wavelengths

Physical mechanisms those interplay in generating super continuum from femto-second pulses propagated through photonic crystal fiber (PCF) have been investigated here. We compare spectrums from two distinct PCFs with different group velocity dispersion profiles to determine the most desirable spectral features such as stronger and ripple free output spectra at wavelength regions of interest, specifically around near infrared wavelength which we can use for coherent anti-Stokes Raman Scattering microscopy of lipid-rich structures. Coherency of the pulses from these two PCFs was also compared. The spectrums from theoretical model will provide us guidance for future experiments.

Supercontinuum generation in highly nonlinear hexagonal photonic crystal fiber at very low power

Abstract. We present the design of a photonic crystal fiber which promises to yield very large optical nonlinearity ∼151  W−1  km−1 at 1.55  μm wavelength. The fiber possesses two zero dispersion points whose locations can be tuned by varying the air hole diameter and hole pitch. The fiber dispersion is anomalous between these two zero dispersion points and its value is moderate. The fiber has been used to numerically simulate optical supercontinuum (SC) generation using low power pump pulses of 50 fs duration at a 1.55-μm wavelength. At the end of 15-cm fiber, SC broadening of about 1200 and 1700 nm can be achieved with pulses of 1 and 5 kW peak power, respectively.

Slow light propagation in tunable nanoscale photonic crystal cavity filled with nematic liquid crystal

Abstract. Slow light propagated through a photonic crystal with a nematic liquid crystal-filled cavity has been simulated and presented. Both slow and fast modes propagate in the waveguide. Design efforts were made to adjust the group velocities of the propagating modes. Numerical studies show that the nematic liquid crystal provides designers an additional degree of freedom to tune the device by using external perturbations such as applying heat or electric field. Comparative studies have also been done to see the performance of the devices built in two different material platforms (silicon and InP). The device can be used as an economic and efficient functional materials system for building robust integrated photonic devices that have the ability to slow, store, and process light pulses.

Using AVHRR-Based Vegetation Health Indices For Estimation Of Potato Yield In Bangladesh

We developed a model correlating Advanced Very High Resolution Radiometer (AVHRR)-based Temperature Condition Index (TCI) and Vegetation Condition Index (VCI) with potato yield in Bangladesh. Weekly TCI and VCI Indices for 1993–2005 along with official potato yield statistics were used for model development. We found a strong correlation between inter annual variation in potato yield and TCI and VCI during the critical period of potato growth (vegetative phase and tuber initiation), mid-December to mid-January. Principal component regression (PCR) was used to construct a model to predict potato yield as function of TCI and VCI. The model explained about 75% of yearto- year variation in potato yield. Remote sensing offers valuable and readily obtainable information on potato yield well in advance of harvest.

Solitary wave propagation in tunable liquid crystal-filled dual-core photonic crystal fibers

ABSTRACT In this paper, we introduce the mathematical model and the necessary constraint conditions of solitary wave propagation through dual core photonic crystal fibres (PCF) filled with liquid crystal. Using the Ansatz method, we derived analytically the necessary formulas to support soliton wave propagation in the new proposed type of coupled bi-refringent fibres. We evaluated dispersion and coupling coefficients by solving wave equations using the vector finite element method. These values can be tuned either by applying external perturbations such as heat or electric field or even altering the geometry of the PCF. Based on the constraint conditions derived from analytic formulas and numerical simulation, we determined the wavelength range for which the soliton waves will be supported without any distortion. The wavelength range can be adjusted by tuning the PCF.