ABOUT THIS CHAPTER

Scientists pick lasers for their experiments for the same reason that engineers pick lasers for the equipment they design-the characteristics of laser light offer some special advantages. Lasers have been used in many types of scientific research since the first laser was demonstrated. It is impossible to cover all the ways that lasers are used in research, so this chapter only samples the high points.

13.1 LASERS OPEN NEW OPPORTUNITIES

The coherent, highly directional, monochromatic, and intense beam from the laser opened new opportunities for scientists and, like engineers and physicians, soon after the first laser was demonstrated, they lined up to borrow, buy, or build their own lasers and test them in their laboratories. They soon began getting interesting results.

One important example was harmonic generation. Physicists had known that the nonlinear interaction of electromagnetic waves with matter could generate harmonics of the fundamental frequency. However, the effect was very small at low intensities, so it had been impossible to observe at the high frequencies of light waves, until the laser came along. A year after Maiman demonstrated the ruby laser, Peter Franken focused ruby pulses into quartz and observed a feeble emission at 347 nm in the ultraviolet, the second harmonic of the ruby 694-nm wavelength. The second-harmonic spot looked so faint on the photograph that a production editor at the journal that published Franken's paper thought it was a flaw and removed it, but Franken had nonetheless made a breakthrough. Today, nonlinear optics is a powerful tool, and harmonic generation is routinely used to generate light at many wavelengths, like the green of green laser pointers.

Many other research advances followed, some important enough to be rewarded with Nobel Prizes. Charles Townes, Nikolai Basov, and Alexander Prokhorov were the first to share one, the 1964 physics prize for developing the principles behind the maser and the laser. (Basov and Prokhorov were recognized for pioneering theoretical work on microwave masers.) Four of the ten physics prizes awarded between 1997 and 2006 were for laser-related work. Table 13-1 lists all laser-related Nobel Prizes through 2007.