Future Developments In Laser Technology And Their Applications

Abstract One of the many areas in which lasers are beginning to play an important role is that of chemistry. One application of great significance is the use of low average power tunable lasers as an analytical tool to measure or study reaction kinetics and products. The other application of equal or greater importance is the use of high average power tunable lasers as a manipulative tool to control or drive chemical reactions in industrial processes. Here the cost of photons is the most important factor and a new device called the "Free Electron Laser" is under development which promises to reduce the photon cost to less than one dollar per pound of material, thus including a wide range of industrial products.TextSoon after the invention of the laser in 1961, predictions were made that the laser would produce a new technological revolution similar to that due to the rapid development of solid state electronics after the invention of the transistor. However, these predictions were slow in being realized due to the much great complexity and cost of lasers and their associated technology, and due to the lack of well-developed need in the optical industry which the laser could satisfy. In fact, the laser was referred to as a solution looking for a problem.Today, these early predictions are coming to pass as both the laser technology and its applications in the scientific and industrial field are developing at a rapid pace. The laser is finding broad uses in such diverse areas as communications, chemistry, biology and medicine, cutting drilling and welding for hardware fabrication, fusion research, isotope separation, metrology, pollution monitoring, surveying, industrial process instrumentation and control, and military uses, to name a few, and the list still is expanding. To a great extent, the applications are limited by the capability of well engineered laser hardware which can be used reliably without being a laser physicist, but this area is improving rapidly.One of the most interesting of the areas just mentioned, in which lasers are starting to play an excit­ ing role, is that of chemistry. Some of the laser tools needed are now available as off-the-shelf items and new ones now in the development process will become available in the next several years as the demand increases.The two general types of laser applications in chemistry are the laser's use as an analytical tool and its use as a manipulative agent, whose object is to induce chemical change. Both applications have been made possible through the development of tunable lasers. In the infrared, this has been achieved through the use of diode lasers, line tunable and high pressure gas lasers and by parametric oscillators, in the visible by dye lasers and in the UV by eximer lasers, and a recent addition, the color center lasers. For very high power applications, a new candidate on the horizon is the free electron laser which can, in principle, be constructed to operate over continuously tunable wide frequency bands from millimeter wave­ lengths to far ultraviolet wavelengths.The extremely high resolution spectroscopy obtainable with lasers is illustrated in Figure 1, where a single P branch rotational line of the complex molecule, uranium hexafluoride, is resolved into its 11 sub­ components due to Coriolis splitting of its degeneracy. Not only are such measurements able to obtain the force constants of the molecule, and give structural information, but they have also permitted the selec­ tion of the correct theoretical model1 and allowed an extension of the theory which permitted accurate predictions of the line intensities as shown by the bars. These measurements were taken in absorption us­ ing a diode laser on flow cooled UFe. The laser intensity available also permits saturation of the medium, which, with the addition of a second tunable laser permits spectroscopy of excited states.Mode-locked dye lasers operating in the visible, and parametric oscillators, (pumped by mode-locked yag lasers) operating in the infrared, are used to produce very short, high intensity pulses at tunable wave­ lengths. These probes permit the study of chemical kinetics by observing fluorescent radiation from the reaction products. Again, a second tunable probe laser can be used to obtain information on the rate at which excitation energy from a single mode is transferred to other modes in the same molecule or is trans­ ferred to other molecules.