INVESTIGATION OF OLIVE OIL AS A PHOTONIC LIQUID CRYSTAL FOR OPTICAL COMMUNICATION SYSTEM

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INVESTIGATION OF OLIVE OIL AS A PHOTONIC LIQUID CRYSTAL FOR OPTICAL COMMUNICATION SYSTEM

ABSTRACT

This project introduces a prospective material for photonic laser applications. The material is olive oil which is classified as organic compound, having a good nonlinear optical properties candidate to be used in photonic applications. Many organic compounds that olive oil is contained, phospholipids, cholesterol, glycolipids, fatty acids compound which are able to behave as lyotropic liquid crystal. So, these compounds are characterized by wide photonic applications. A high purity sample of olive oil has been subjected to spectrophotometer to determine the absorption spectra. Then, the nonlinear optical properties represented by nonlinear refractive index and nonlinear absorption coefficient are determined using a highly sensitive method known as z-scan technique. z-Scan experiment was performed using a CW Nd:YAG and SHG Nd:YVO4 lasers in two parts. The first part has been done using a closed aperture placed in front of the detector to measure the nonlinear refractive index at two wavelengths (1064nm and 532nm) and versus incident powers at 1064nm. The second part was done using an open aperture to measure the nonlinear absorption coefficient at two wavelengths (1064nm and 532nm) for different incident powers at 1064nm.

CHAPTER ONE

INTRODUCTION

  • Background of the study

 

Liquid crystals (LCs) are organic materials that are liquid but that show a certain degree of ordering (positional and/or orientational). With this definition, many materials can be classified as liquid crystals, but the majority of liquid crystals that are used in photonic applications are of the thermotropic type. Thermotropic means that the liquid-crystal phase exists within a certain temperature interval (in contrast to lyotropic materials for which the material is liquid-crystal within a certain concentration range). Various types of thermotropic liquid-crystal materials exist, and many differ- ent mesophases have been discovered in the last decades: nematic, smectic A, smectic C, columnar, blue phases, and many many more. The diversity of liquid-crystal materials is huge, but this diversity is even overshadowed by the number of applications in which liquid crystals are used nowadays. The majority of applications are related to information- display applications. Liquid crystals have conquered the major market share in different display application areas: television screens, laptop screens, screens in mobile phones, etc. Only in projection displays does a tough competitor exist, namely micro electromechanical systems or licenced by Texas Instruments: Digital light processing. Organic light emitting diodes (OLEDs) are the obvious next generation technology that could overtake the LC domination, but today OLED displays have not penetrated the market and only the future will tell if they will. In this review article, we will focus on nondisplay applications, but because we cannot go too broad, we restrict ourselves to photonic applications in which the light is actively manipulated by the LC. In this re- view article, a certain external influence (surface anchoring, electric fields, optical fields) is used to (re)orient the LC in a certain way. In turn, the LC then changes the light that is propagating through it. Of course, as in every review article, it is impossible to list all the fascinating new scientific results or breakthroughs. Therefore, the authors apologize for not including some novel exciting phenomena or applications such as light-induced switching of LC polymers1–3or  novel retardation structures such as broadband cholesteric filters [4] .

Organic materials are applied in nonresonant photonic applications because these materials can show very high nonlinear coefficients, high damage threshold and good transparency at short wavelengths. In 2007 Omer Namer [1] investigated experimentally and theoretically that the olive oil can be categorized as an organic dye, which can be used as an active laser material. One of these investigations showed that the olive oil behaves as a nonlinear material where it has a ”blue shift” in some excited wavelengths. Therefore, the nonlinear optical properties of olive oil which are of prominent importance for photonics applications have been found in this research. Lyotropic liquid crystals are one of liquid crystals obtained by varying the temperature or concentration [2] , which is obtained when an appropriate concentration of material is dissolved in some solvent. The most common  systems  those formed by amphiphilic molecules (molecules posses a hydrophilic part that interacts strongly with water and a hydrophobic part that is water insoluble). The effects of optical nonlinear can be employed for the optical limiting design and its performance. Limiter has a linear transmitted intensity at low input intensities, but above the threshold intensity, its transmitted intensity becomes constant [7] . Materials with strong nonlinear optical absorption properties have been recognized as prospective optical limiting materials for applications such as pulse shaping in various wavelength regions, and sensor protection noise reduction [8] . The main requirements for optical limiting materials are large pulse energy suppression, high damage threshold, high linear transmission, and low turn-on threshold [9] .

 

1.2       Statement of the problem

The olive oil represents the one class of lyotropic liquid crystal in nematic phase [3] . Liquid crystals are optically highly nonlinear materials in that their physical properties (temperature, molecular orientation, density, electronic structure, etc.). These are obtained by an applied optical field. The polarized light beam from laser source can induce an alignment or ordering in isotropic phase. These result in a change in refractive index. In isotropic phase the change in refractive index is due to the density change following arise in temperature. In the nematic phase the change in the refractive index depend directly on the temperature. The reorientation of molecules in liquid crystals depends on the phase of liquid crystals. For the isotropic phase the liquid crystal molecules are randomly oriented owing to thermal motion. So an intense laser field will force the anisotropic molecules to align themselves in the direction of optical field through the dipolar interaction.

1.3       Objective of the study

The general objective of this study is to investigate olive oil as a photonic liquid crystal for optical communication system with the following specific objectives of the study:

  1. To examine the variation in change in refractive index with incidence intensity.
  2. To assess the UV-VIS transmission of olive oil
  3. To examine the peak to valley values of normalized transmittance curves.
  4. To compare the nonlinear refractive index and nonlinear phase shift versus incident power.

1.4       Scope of the study

This study will focus on a high purity sample of olive oil subjected to spectrophotometer to determine the absorption spectra. Then, the nonlinear optical properties represented by nonlinear refractive index and nonlinear absorption coefficient will be determined using a highly sensitive method known as z-scan technique. z-Scan experiment which will be performed using a CW Nd:YAG and SHG Nd:YVO4 lasers in two parts.

INVESTIGATION OF OLIVE OIL AS A PHOTONIC LIQUID CRYSTAL FOR OPTICAL COMMUNICATION SYSTEM

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