I= SOCIO – ECONOMIC CONSEQUENCES OF RETURN MIGRATION AND THE ADJUSTMENT PROBLEMS IN PUNJAB Title of Thesis


Pakistan Research Repository

 

 

 

 

 

 

Title of Thesis

ANALYTICAL INVESTIGATIONS OF NONLINEAR WAVES IN SEMICONDUCTOR SUPERLATTICE PLASMAS

Author(s)

Rashid Ali

Institute/University/Department Details

University of the Punjab, Lahore /Center Of Excellence In Solid State Physics

Session

2000

Subject

Physics

Number of Pages

112

 

Keywords (Extracted from title, table of contents and abstract of thesis)

Nonlinear Waves, Semiconductor Superlattice Plasmas, Helicon Envelope Solitons,

 

Abstract

In the present work we have investigated non-liner wave propagation through semiconductor superlattice plasmas; we have considered different types of layered superlattices or media through which the waves propagate. First of all we consider the propagation of helicon envelope solitons through layered semiconductor superlattice plasma. The non-liner evolution, equation governing the propagation of these envelope solution is the set of Zakharov equations, which are a more generalized form of the Non-liner Scrodinger Equation (NLS). We derive the set of equations, which have a known evelope soliton solution. We use the Kroning-Penney model along with the relevant boundary conditions to investigate propagation of helicon solitons in the layered medium. These boundary conditions are useful for connecting the envelops soliton fields across the layers. We obtain a nonlinear dispersion relation which relates the nonlinear analogue of the Bloch wave number with different parameters. We numerically investigate the dependence of the nonlinear Bloch wave number on the propagation frequency we see that a propagation band and gap structure for the helicon envelope soliton solution in a layered semiconductor plasma. Owing to the recent experimental importance of device fabrication (e.g. amplifiers etc), superconductivity is a subject of investigation for a number of reason. In the second problem we investigate the propagation of density waves in a high-temperature superconducting medium consisting of a finite number of layers. An electromagnetic wave interacts with superconducting electrons to set up charge-density gradients within the superconducting electron plasma. We use the London equations and the two fluid approaches to derive a linear dispersion relations, for the propagation of the density waves within each layer. Once again the Kronig-Penney model is used to model the layered medium and a dispersion relation governing the properties of the charge-density wave in the layered medium. The electromagnetic wave dissipates in the layered superconducting medium. We numerically investigate the dependence of the complex Bloch-wave number on the propagation frequency using the standard boundary conditions. Reflectivity and transmissivity have been discussed for periodic layered structure consisting of a finite number of superconducting layers, we numerically discussed these quantities and their dependence background parameters have been discussed. In the third problem we take the same set of equations and investigate the propagation of nonlinear charge density waves in a superconducting layered structure. It is seen that the nonlinear Schrodinger (NLS) equation governs the propagation in the superconducting plasmas. We investigate the modulational instability of the NLS equation. Subsequently we use boundary conditions of the standard Kronig-Penney model to derive a nonlinear dispersion relation relating the Bloch wave vector to the propagation frequency. This nonlinear dispersion is also numerically investigated. In the last problem, we investigate the propagation of nonlinear coupled electromagnetic waves in a composite medium having properties of ferromagnetic and semiconductor materials. We derive nonlinear evolution equation using reductive perturbation method for which we obtain soliton solution. We also investigate the limiting cases and find that our results reduce to the previously investigated.

 

Download Full Thesis

180.kbs

1639 KB

 

S. No. Chapter Title of the Chapters

Page

Size (KB)

    Table of Contents  

180.kbs
86 KB

1 1 INTRODUCTION 1

180.kbs
166 KB

       
       
       
2 2 HELICON SOLITONS VIA ZAKHAROV EQUATIONS 15

180.kbs

347 KB

 

       
       
       
       
3 3 DENSITY-WAVES IN LAYERED HIGH TEMPERATURE SUPERCONDUCTING PLASMAS 33

180.kbs

558 KB

 

       
       
       
4 4 NONLINEAR DENSITY-WAVES IN LAYERED SUPERCONDUCTING PLASMAS 65

180.kbs

167 KB

 

       
       
5 5 COUPLED NONLINEAR ELECTROMAGNETIC WAVES IN A FERROMAGNETIC-SEMICONDUCTOR MEDIUM

79

180.kbs

237 KB

6 6 CONCLUSIONS

105

180.kbs

46 KB

7 7 REFERENCES

109

180.kbs

64 KB