There are currently several free electron lasers operating in the 1- to 9-µm region of the spectrum, such as those at Duke University, Stanford University, Vanderbilt University, and Los Alamos National Laboratory. (Chapter 2 lists the FELs in the United States and abroad.) Typically, FELs in the infrared wavelength region generate trains of 1-ps micropulses in 0.5- to 6-µs macropulses and produce 100 mJ of energy in a macropulse. Scientists at these facilities and visitors have carried out experiments in tissue ablation and laser surgery and have studied vibrational photon echoes, and they plan studies of the biophysics of large molecules such as proteins. The surgical studies, for example, have explored basic and applied aspects of the interaction of light with tissue to discover the optimum wavelength and pulse width for clinical applications, which are likely to be implemented eventually with conventional lasers. The research advantage of the FEL in this context is its wide tunability and its flexible pulse structures, with the possibility of using chirped pulses being a capability that is unavailable with conventional lasers in this wavelength region.
Cost is one important factor in assessing free electron lasers and other coherent light sources, particularly if one is considering establishing a center for shared use of a large device. Because conventional lasers are so ubiquitous and productive, the spending on research lasers in the United States is one point of comparison. An annual survey of worldwide laser sales (Laser Focus) found that in 1993 (the last year for which figures are available) the worldwide market for lasers used in research and development was $110M. The committee learned from two large scientific laser companies (Spectra Physics and Coherent) that the average fraction of their sales of lasers for scientific research in the United States is 34%, and, thus, it estimates that the annual expenditure on laboratory research lasers in this country is about $37M. The distribution of this amount among types of laboratories is roughly 44% for universities, 35% for industrial laboratories, and 21% for government laboratories. These laboratory lasers cost between $5K and $250K, with $100K being the cost of a typical system.
Laboratory lasers have been and will continue to be an important photon source for research in the region from 10 µm to 200 nm. Much of the science in this wavelength region involves simultaneous use of several sophisticated laboratory lasers. When cost and convenience are considered, it is unlikely that free electron lasers will be competitive with laboratory lasers in this spectral region in the foreseeable future.
In the near-infrared, visible, and ultraviolet regions, continued support of lasers in individual investigators' laboratories is the highest priority.