Introduction
Optics, the study of light, is the second oldest science (astronomy is the first). Yet at the
beginning of the Twenty-First century it has the energy and dynamism of youth. Exciting
experimental discoveries and theoretical insights continue to put optics at the forefront of modern
research. A revolution occurred in 1960 with the development of the laser, a compact source of
spectrally pure, focused, virtually noise-free light. The consequences of that revolution are still
unfolding.
We are all familiar with the use of lasers as bar-code scanners and as operating devices in
compact disk players, although most people are unaware of how these devices actually work. In
fact, lasers today are used for a broad variety of tasks. From the “low-tech” application in which
laser light replaces the traditional rope and chains used by surveyors to lay out a long straight
line, to “high-tech” application in which laser light is used to slow down and cool a beam of
atoms. Other applications of the laser include:
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A communications medium in high-speed fibre-optic cables.
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A precision scalpel for delicate surgery.
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Pollution monitoring in the air via light scattering
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Studying the details of chemical reactions using femtosecond pulses
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As a tool for atomic physics to selectively excite atomic states
Lasers are used to produce entirely new states of matter, so-called “phaseonium”, with bizarre
optical properties. They have also been used to produce quantum objects of macroscopic size,
allowing direct investigation of the weird predictions of quantum mechanics, and as “optical
tweezers” to move individual atoms.
And most investigators are agreed that the era of the laser is just beginning.
Lasers operate according to a few simple principles that we will study in this course. Essentially,
a laser requires an optical medium capable of storing energy in long lived excited states of atoms,
molecules, or crystals; an efficient way of turning this energy into radiation at the appropriate
wavelength; and a specially designed cavity within which electromagnetic oscillations can be
sustained and amplified. The course is designed to provide the physical background for
understanding what the previous sentence means
This is a course in physical optics that covers traditional and modern topics and presents the
background necessary for understanding laser operation and the characteristics of laser beams.
Physical optics, of course, has many other applications than those associated with lasers and
these are not slighted. While the course addresses many questions relevant to laser performance it
is not a formal course in laser physics. Such a course would be a natural successor to this one.
After a consideration of laser safety the course covers the mathematics of waves, in particular the
use of complex numbers to represent the amplitude of oscillating quantities. The polarization
concept provides a direct application of these ideas. This is followed by a discussion of the
1.1
optics of thin films. One of the most important applications of thin films in the optics laboratory
is the beam splitter. A careful discussion of the beam splitter is presented and is followed by a
section on the use of beam splitters in interferometers. Freely propagating light is covered next,
beginning with diffraction phenomena. Interference via wavefront division ends this section. The
properties of optical gratings are an important application.
We next discuss the elements of thermal and atomic spectra. Work with prism and diffraction
grating spectrometers culminates in use of an electronic spectrometer (the pc spectrometer made
by Ocean Optics). Subsequently, fluorescence is covered because of the background it provides
for understanding lasing media.
At this point the stage has been set for laser physics. We cover the Schalow-Townes theory of an
optical resonator, discuss factors influencing the gain in lasing media, and investigate the
longitudinal modes of a gas laser.
Following this work, we investigate the Michelson and Fabry-Perot interferometers. Coherence
concepts are introduced in the course of that work and the notion of fringe visibility is explored
The course then proceeds to a discussion of phase masks, zone plates and holography..
1.2