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Lasers Invention to Application (1987) / Chapter Skim
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The Laser: Still Young at 25?
Pages 1-16

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From page 1...
... Although not yet of the economic importance of conventional electronics, the laser industry is significant and growing. This paper will provide a brief review of the history of the laser; describe some of the characteristics and performance capabilities of different types of laser devices; give a short introduction to the breadth and diversity of laser applications; and finally, summarize some of the exciting current accomplishments and possible future advances in laser technology.
From page 2...
... Maiman produced this first laser action by placing silver mirrors directly on the end of a synthetic crystal of ruby, and then pumping or exciting this crystal with an intense flash of light from a standard photographic flash lamp. Maiman's pioneering advance was rapidly followed by the development of a number of other laser devices by the IBM and Bell Telephone Laboratories; in particular, the first continuously running, electrically pumped gas lasers were developed in the same year at
From page 3...
... Schawlow demonstrating that a flash of red light from a small ruby laser breaks the dark-colored inner balloon without damaging the transparent outer balloon. This procedure exactly mimics the way laser light can be used to repair a detached retina inside the eyeball, make a weld inside a closed vacuum chamber, or trigger a chemical reaction inside a closed chemical cell.
From page 4...
... In all cases, however, its essential function is to excite or lift some of the laser atoms out of their lowest quantum energy level and into upper energy levels (see Figure 2~. If atoms can be excited into upper energy levels and, more importantly, a condition of population inversion can be achieved, in which more atoms are excited into some upper atomic level than into some lower atomic level, then laser action can occur.
From page 5...
... FIGURE 2 (a) A collection of laser atoms and their quantum energy levels.
From page 6...
... How many gold medals might the laser, in particular, win in such a competition? FREQUENCY RANGE, TUNING RANGE, AND BANDWIDTH Laser devices of many different kinds will clearly win all the available gold, silver, and bronze medals for frequency range, tuning range, and instantaneous bandwidth.
From page 7...
... Without going into further detail here, it should also be noted that an ordinary dye laser with a 200-A spectral width has a frequency bandwidth sufficient to transmit the equivalent of one simultaneous telephone channel for every person on earth. PEAK POWER For setting peak power output records, laser devices also stand absolutely supreme, in large part because of their ability to generate very short pulses.
From page 8...
... Israeli scientists have TABLE 2 Laser Pumping Methocis Pumping Method Laser Action Optical pumping Laser materials pumped by flash lamps, arc lamps, tungsten lamps, exploding wires, light-emitting di odes, flames, focused sunlight, other lasers Gas discharges Direct electron and collisional excitation in glow dis charges, arc discharges, hollow cathode discharges Chemical reactions Laser action following chemical mixing, flash photoly sis, flame photolysis Direct electrical Direct electrical excitation in semiconductor injection lasers, electron beam-pumped solids and gases Gas-dynamic lasers Laser action derived from hot gases, supersonic expan sions, shock fronts Plasmas Laser action in plasma pinches, laser-induced plasmas Nuclear reactions Fission fragment pumping of gas lasers Nuclear explosions Atomic bomb-pumped x-ray lasers Natural lasers Sunlight, interstellar radiation, particle beams
From page 9...
... Many commonly used lasers are also, unfortunately, far less efficient in the use of electrical input energy than would be desirable. The common small helium-neon laser has a typical operating efficiency of only a small fraction of a percent, although there are also useful types of gas and semiconductor lasers that have efficiencies of 60-70 percent from direct electrical input.
From page 10...
... Certain laser oscillators can, however, have a spectral purity and absolute frequency stability so extraordinary that just in the past few years the international standards for both frequency and time have been, by definition, unified into a single laser device. That is, the new standards for both distance and time are now provided by a certain ultrastable laser oscillator transition located in the middle infrared region of the spectrum.
From page 11...
... Given the narrow beams and high peak powers of lasers, laser radar echoes are routinely obtained from optical reflectors located on the moon, with accumulated range accuracies of a few centimeters in the distance to the moon. By making such laser-ranging measurements to a cooperative orbiting satellite simultaneously from multiple stations, it is possible first to determine the satellite orbit and its perturbations with great accuracy and then to determine the relative positions of the laser stations on earth, and thus to map the earth with comparable accuracy even across seas and oceans.
From page 12...
... For example, laser beams are projected into huge wind tunnels to measure local flow velocity and turbulence. Lasers are extraordinary tools for identifying materials as well.
From page 13...
... All of these commercial, industrial, and home applications of laser devices, however diverse and ingenious, thus far have been only preliminary. Indeed, the worldwide sales of laser devices in 1985 totaled only about $400 million-$500 million—or about a quarter of the sales of small computers in the same period by Apple Computers alone.
From page 14...
... The free electron laser may, with further development, also provide a similarly useful source in the visible and ultraviolet regions of the spectrum. FEMTOSECOND OPTICAL PUlSES, BISTABILITY, CHAOS, AND SOLITONS The incredible advances made in femtosecond laser pulses during the past few years represent one example of progress in the field.
From page 15...
... Because the properties of the electrons in these multiple quantum well structures can differ greatly from ordinary materials, the electronic and optical properties of these materials offer remarkable new capabilities, including much faster forms of conventional electronic devices. In optics, the result has already been much more efficient and shorter wavelength diode lasers for use in fiber-optic communications or audio compact disc players, as well as improved photodetectors, light modulators, and other electro-optic devices.
From page 16...
... Nonetheless, Lawrence Livermore Laboratories has recently announced the observation of stimulated emission and laser amplification in the far-ultraviolet or soft x-ray region, at wavelengths of 150-200 A, in a target plasma pumped by a highpower laser beam. The same lab has also produced a true, if short-lived, one-shot x-ray laser in the few-angstrom region by pumping a suitable laser material directly with a small nuclear explosion.


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