Optical Properties of Materials

Unit – IV

Chapter - 4

Optical Properties of Materials

Classification of optical materials Optical processes in semiconductors: optical absorption and emission, charge injection and recombination, optical absorption, loss and gain. Optical processes in quantum wells - Optoelectronic devices: light detectors and solar cells light emitting diode laser diode optical processes in organic semiconductor devices -excitonic state Electro-optics and nonlinear optics: Modulators and switching devices plasmonics.

Introduction

The optical characteristics of materials are determined by the type of interaction between the electromagnetic radiation and the electrons of the atoms in the material.

We see many of the common optical characteristics of materials such as their colour, brightness, transparency, reflectivity etc.

Besides, these common properties, there are many more special optical properties of materials which make them useful in a wide range of optical devices.

Some of the commonly used optical materials and devices are window glasses, lenses, mirrors, antireflection coatings etc.

Some of the most recently developed high-technology optical devices are lasers, optical fibers, photodiodes, optical memories (CD-ROM), electro-optic modulators.

Definition

The materials which are sensitive to light are known as Optical materials. These optical materials exhibit a variety of optical properties.

CLASSIFICATION OF OPTICAL MATERIALS

Generally, optical materials are classified into three types based on the nature of propagation of light namely,

(i) Transparent

(ii) Translucent

(iii) Opaque

(i) Transparent

Transparent materials are the materials which transmit the light with little absorption and reflection. These materials are transparent in nature and hence, one can clearly view the object through the material.

bris Electrical insulated materials are transparent. Similarly, few semiconducting materials are also transparent.

(ii) Translucent

The incident light gets scattered within the materials and hence, the diffused light is transmitted with the other side of the materials.

One cannot clearly view the object while viewing through the materials. These materials are known as translucent material.

(iii) Opaque

The material which absorbs the visible light is termed as opaque. When an electromagnetic radiation in the entire visible spectrum is incident on this material, either it gets reflected or absorbed.

Thus, the materials are opaque. Few semiconducting materials also exhibit this opaque nature.