From Modern Optical Engineering: The Design of Optical Systems, Fourth Edition

10.1 Reflection, Absorption, Dispersion

To be useful as an optical material, a substance must meet certain basic requirements. It should be able to accept a smooth polish, be mechanically and chemically stable, have a homogeneous index of refraction, be free of undesirable artifacts, and of course transmit (or reflect) radiant energy in the wavelength region in which it is to be used.

The two characteristics of an optical material which are of primary interest to the optical engineer are its transmission and its index of refraction, both of which vary with wavelength. The transmission of an optical element must be considered as two separate effects. At the boundary surface between two optical media, a fraction of the incident light is reflected. For light normally incident on the boundary the fraction is given by


where n and n' are the indices of the two media (a more complete expression for Fresnel surface reflection is given in Chap. 11).

Within the optical element, some of the radiation may be absorbed by the material. Assume that a 1-mm thickness of a filter material transmits 25 percent of the incident radiation at a given wavelength (excluding surface reflections). Then 2 mm will transmit 25 percent of 25 percent and 3 mm will transmit 0.25 0.25 0.25 = 1.56 percent. Therefore, if t is the transmission of a unit thickness of material, the transmission through a thickness of x units will be given by



Products & Services
Ball Lenses
Ball lenses are used to provide short focal lengths for use with collimated light and are often used in fiber coupling applications.
Linear Polarizers
Linear polarizers transmit light waves along one axis and absorb them along the other. The transmitting and absorbing axes of linear polarization are oriented at 90 degrees to each other.
Optical Prisms
Optical prisms are blocks of optical material with flat, polished sides that are arranged at precisely controlled angles to one another. They are used in optical systems to deflect or redirect beams of light. They can invert or rotate images, disperse light into component wavelengths, and separate states of polarization.
Optical Lenses
Optical lenses are transparent components made from optical-quality materials and curved to converge or diverge transmitted rays from an object. These rays then form a real or virtual image of the object.  This area includes micro lenses.
Specialty Optical Fiber
Specialty optical fiber is modified, usually by doping, for a specialized function. It consists of one or more transparent fibers enclosed in a protective covering.

Topics of Interest

11.1 Dielectric Reflection and Interference Filters The portion of the light reflected ( Fresnel reflection) from the surface of an ordinary dielectric material (such as glass) is given by (11.1)...

Absorption: The portion of optical attenuation in an optical fiber resulting from the conversion of optical power to heat; caused by impurities such as hydroxyl ions in the fiber. A/B Switch: A...

8.1 Refractive Index of Porous Silicon W. Theiss and S. Hilbrich May 1997 A INTRODUCTION The complex refractive index (usually denoted as = n + i ?) determines how light waves propagate inside a...    Basis of Phased Array Beam Steering    The alteration of an incident optical wavefront by phase variation is characterized by considering the effect...

2.7   PROPAGATION OF LIGHT As already described, when light enters matter, it is reflected by its surface and refracted by the matter, and its velocity changes as well as its wavelength, but not...