Lasers invention

National Academy of Sciences. (1987). Lasers Invention to Application. Washington, DC National Academy Press. 

The first laser produced was the ruby laser, invented in 1960. Rubies are crystals of aluminum oxide (corundum, AI2O3), containing about 0.5% chromium ions Cr3+, as substitution impurities, CrA, and laser action, as well as color, is entirely due to these... 

Noise contribution from the many modes in the Stokes laser can be reduced by the use of a modeless dye laser invented by Ewart [67]. Fortunately nitrogen CARS spectra are less affected by this due to the large number of spectral lines that can be probed together [68]. 

Lasers. The term laser is an acronym for light amplification by stimulated emission of radiation. The possibility of lasers was postulated by Albert Einstein, and a microwave laser was developed in the 1950 s. Some credit American physicist Gordon Gould with the invention of the first laser using light however the ruby laser invented by American physicist Theodore Maiman in 1960 is considered to be the first laser to use light. 

It is said that necessity is the mother of invention. This adage says volumes about the early development of the laser. Unring World War II, U.S. mihtaiy and civilian scientists searched frantically for improved radar. Wliile these researchers met with only mixed success, their efforts spurred basic research. After the war, using knowledge gained from this line of inquiiy, the first successful laser was developed in 1960. 

The laser has revolutionized many aspects of science and other disciplines, as well as the daily lives of millions of people. When it was first invented, the laser was referred to by some as a solution looking for a problem because it came about mostly from basic research rather than the active solution to a particular concern. At the time, no one could have predicted the far-reaching effects it would have in the second half of the twentieth centuiy, or that it would come to be considered by many as one of the most inQuen-tial technological achievements of that time. 

There are countless other reactions, many like these and others rather different, but the idea in every case is the same. A sudden flash of light causes an immediate photo-excitation chemical events ensue thereafter. This technique of flash photolysis was invented and applied to certain gas-phase reactions by G. Porter and R. G. W. Nor-rish, who shared with Eigen the 1967 Nobel Prize in Chemistry. High-intensity flash lamps fired by a capacitor discharge were once the method of choice for fast photochemical excitation. Lasers, which are in general much faster, have nowadays largely supplanted flash lamps. Moreover, the laser light is monochromatic so that only the desired absorption band of the parent compound will be irradiated. 

There are many potential paths for revitalizing old methods of test using new array detectors and powerful processors. The only reason most testing is done by unequal path interferometry is due to the invention of the HeNe laser. If its development had been delayed a year or two and computing capabilities had been a little more advanced, most optical testing would be done with slope measuring, common path techniques that are less sensitive to the environment. 

The first Raman and infrared studies on orthorhombic sulfur date back to the 1930s. The older literature has been reviewed before [78, 92-94]. Only after the normal coordinate treatment of the Sg molecule by Scott et al. [78] was it possible to improve the earlier assignments, especially of the lattice vibrations and crystal components of the intramolecular vibrations. In addition, two technical achievements stimulated the efforts in vibrational spectroscopy since late 1960s the invention of the laser as an intense monochromatic light source for Raman spectroscopy and the development of Fourier transform interferometry in infrared spectroscopy. Both techniques allowed to record vibrational spectra of higher resolution and to detect bands of lower intensity. 

Binnig et al. [48] invented the atomic force microscope in 1985. Their original model of the AFM consisted of a diamond shard attached to a strip of gold foil. The diamond tip contacted the surface directly, with the inter-atomic van der Waals forces providing the interaction mechanism. Detection of the cantilever s vertical movement was done with a second tip—an STM placed above the cantilever. Today, most AFMs use a laser beam deflection system, introduced by Meyer and Amer [49], where a laser is reflected from the back of the reflective AFM lever and onto a position-sensitive detector. 

The determination of the laser-generated populations rij t) is infinitely more delicate. Computer simulations can certainly be applied to study population relaxation times of different electronic states. However, such simulations are no longer completely classical. Semiclassical simulations have been invented for that purpose, and the methods such as surface hopping were proposed. Unfortunately, they have not yet been employed in the present context. Laser spectroscopic data are used instead the decay of the excited state populations is written n (t) = exp(—t/r ), where Xj is the experimentally determined population relaxation time. The laws of chemical kinetics may also be used when necessary. Proceeding in this way, the rapidly varying component of AS q, t) can be determined. 

Fundamentally, the properties of laser light are concomitants of its coherence, which is in turn a consequence of the nature of stimulated emission. Most of these properties, especially brightness, monochromaticity, directionality, polarization, and coherence itself, are useful (for many applications, indis-pensible) in a spectroscopic light source. The spectroscopic potential of lasers was recognized even before they were invented. Actual applications remained very specialized until tunable lasers were devised. 

With the invention of the laser in 1960 and the subsequent development of pulsed lasers using Q-switching (Chapter 1), monochromatic and highly-collimated light sources became available with pulse durations in the nanosecond timescale. These Q-switched pulsed lasers allow the study of photo-induced processes that occur some 103 times faster than events measured by flash lamp-based flash photolysis. 

Since the field of spectroscopic laser applications is so vast and the number of published papers exceedingly large, this review cannot be complete. However, the author has tried to give a reasonable survey of what has been done and to offer some ideas about what can be done in modem spectroscopy with such an interesting and stimulating invention as the laser (Light Amplification by Stimulated Emission of Radiation). 

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