Atomic, Molecular, and Optical Physics (1986) / Chapter Skim
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6 Optical Physics
6 Optical Physics
Pages 110-125
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From page 110... ...
The distinction between optical physics, applied physics, and optical engineering is blurred, for devices and applications are close companions to basic research in this area of physics. The first two sections of this chapter deal with lasers and laser spectroscopy topics that have transformed optical science.
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From page 111... ...
Continuous-wave dye lasers achieve a stability and resolution far exceeding those of traditional light sources improvements by factors of hundreds to hundreds of thousands are typical. (See Figure 6.1.)
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From page 112... ...
Although this highly stabilized system is at the benchtop stage in a research laboratory, industry has been very effective in making advanced laser and optical technologies available rapidly. (Courtesy of the Joint Institute for Laboratory Astrophysics.)
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From page 113... ...
To illustrate the role of AMO physics in the development of lasers, we have chosen one device the excimer laser to describe in some detail. Excimers and Excimer Lasers Excimers are diatomic molecular systems for which the electronically excited state is tightly bound but the ground state is a very loosely bound, essentially unbound, van der Waals molecule.
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From page 114... ...
Beyond this, a new optical technology has emerged, combining atomic, molecular, and optical science and leading to innovations such as optical frequency standards, new light conjugators, four-wave mixers, and far-infrared detectors. The collective enterprise has come to bee called laser spectroscopy.
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From page 115... ...
Ultrasensitive Spectroscopy Lasers make it possible to observe extraordinarily weak absorption of light using a variety of simple techniques. For instance, by placing a small sample of a gas such as ordinary air inside the resonator of a dye laser, strong yellow absorption bands of water vapor and molecular oxygen appear in the laser's light.
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From page 116... ...
This measurement represents an important spectroscopic advance because its intrinsic linewidth is more than a million times narrower than for normal optical transitions. It provides the opportunity to measure the Lamb shift in the ground state, and the wavelength can be directly related to the Rydberg constant and the electron-proton mass ratio.
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From page 117... ...
Gaseous and solid atomic systems can be coherently excited, producing a new and unusual class of nonlinear optical phenomena. Effects such as optical free-induction decay the coherent emission from atoms excited by a single-laser pulse and photon echoes the delayed burst of coherent radiation following excitation by two successive laser pulses can be applied to study dynamic interactions of atoms in their local environment.
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From page 118... ...
The ions are observed by their fluorescence under laser light. The photograph at bottom left shows the laser light scattered by a small cloud of trapped ions.
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From page 119... ...
The method, which is made possible by the use of a dye laser with a 100-Hz linewidth, has been applied to study the optical Bloch equations, the starting point for many theories in quantum optics. It has been found that in intense laser fields the optical Bloch equations must be modified because the radiation inhibits the linebroadening ejects of nuclear magnetic interactions.
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From page 120... ...
CARS studies have been performed in hostile environments such as the combustion chamber of internal combustion engines, in gas-turbine combustors, and even in jet engine exhausts. Other applications for the coherent Raman techniques include studies of the energy-level distributions that result from optical photodissociation, trace detection of pollutants in gas and liquid phase, the spectroscopy of biological molecules, plasma diagnostics, and applications in the study of hydrodynamic flow.
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From page 121... ...
Many of the dynamical phenomena that have been studied in lasers, for instance fluctuations and regenerative pulsations, can be observed under far better controlled conditions using optically bistable devices. The transition from ordered to chaotic motion is of particular interest.
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From page 122... ...
Optical bistable devices provide a way to study the transition from regular to chaotic motion in reproducible experiments that can be carried out at very high speed. The simplest bistable optical system comprises two mirrors and a nonlinear medium that is operated in a transient mode using pulsed lasers.
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From page 123... ...
Rydberg Atoms and Cavity Quantum Electrodynamics Any neutral atom in which one electron is in a high-lying energy level is known as a Rydberg atom. These atoms have opened a new area in the study of fundamental radiative processes cavity quantum electrodynamics.
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From page 124... ...
The ability to observe basic radiative processes with Rydberg atoms offers a new arena for studying electrodynamic phenomena. Although quantum electrodynamics is usually regarded as a highly developed theory, the new experiments suggest that there is a wide body of phenomena yet to be discovered.
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From page 125... ...
Femtosecond spectroscopy can provide revolutionary insights into the dynamics of molecules and solids, and into chemical reactions, since femtosecond pulses are compared to the characteristic times for all of these. For instance, a molecule typically requires 1o-~4 to 1o-~3 second to vibrate; the time for electrons in a semiconductor to equilibrate after they have been excited can be as short as 1o-~4 second; and proton and electron transfer in molecules can be quicker than 1o-~4 second.
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