Photonics Crystal Fibers



By

CHAPTER 1: INTRODUCTION1

Introduction1

Theory1

CHAPTER 2: LITERATURE REVIEW3

Introduction3

Manipulating the microscopic world6

Nanofabrication with optical tweezers11

Optical actuators13

The Proposed Method15

Photonic Bandgap Structures18

CHAPTER 3: METHODS26

Introduction26

Methods26

Calculation27

Functioning27

CHAPTER 4: RESULTS AND DISCUSSION34

Introduction34

Experimental set-up37

Principle of the method and experimental implementation48

CHAPTER 5: CONCLUSION51

Fabrication of air-core photonic crystal fibres55

Demonstration of Gas Sensing59

BIBLIOGRAPHY62

CHAPTER 1: INTRODUCTION

Introduction

Photonic Crystal Fibers (PCF), which are optical fibers with a cross-sectional microstructure of air holes and/or doped sections, have in recent years attracted much scientific and technological interest. PCFs offer a number of novel design options, such as very large or very small mode areas, high numerical aperture, guidance of light in air, and novel dispersion properties .

Based on pure silica glass, the invention of single material photonic crystal fiber also known as holy fibers (HFs) or microstructure fibers has attracted wide interest over the past few years. The air-filled holey cladding leads to unique guidance properties such as photonic band-gaps at optical wavelengths, very-large-core with endless single mode guidance and soliton effects, polarization maintenance and high birefringence and dispersion management arise and promise various novel applications.

Theory

The core of the PCF is made of solid silica and the cladding consists of multiple layers of air holes separated by narrow silica bridges. The idealized structure of the PCF have regular hexagonal array of perfectly circular air holes. In recent years, photonic crystal fiber made of pure silica and air holes provided a new approach of dispersion

compensation: large negative dispersion (D) can be achieved in PCF due to high relative difference (?) between air and silica, and can be tailored by the size and structure of air holes in the cladding . To determine the dispersion parameters in the conventional fiber the most important thing that must be fixed is the relation between the normalized propagation constant (B), and the V-number. The formula of the normalized propagation constant is given by :

where is the propagation constant and must be within the range (kncl = = knco), k is the wave number (k=2p/), is the wavelength while nco and ncl are the core and the cladding index, respectively. Due to the high similarity between the ncl and neff most researchers assume that they are the same. On the other hand, formulation of the V-parameter suggested to be based on an approximation with an equivalent step index (SIF). In the case of a SIF, the V-parameter, VSIF, as function of wavelength,, is given by :

CHAPTER 2: LITERATURE REVIEW

Introduction

Optical tweezers use the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometres to tens of micrometres. Since their introduction in 1986, the optical tweezer has become an important tool for research in the fields of biology, physical chemistry and soft condensed matter physics. Recent advances promise to take optical tweezers out of the laboratory and into the mainstream of manufacturing and diagnostics; they may even become consumer products. The next generation of single-beam optical traps offers revolutionary new opportunities for fundamental and applied ...