A far-infrared free electron laser user facility capable of producing picosecond pulses should be established. Such a facility could be a new construction or a modification of an existing facility. The committee believes that the scientific opportunity justifies the establishment of such a facility.
Such a facility should have a means of synchronizing a second tunable laser with the free electron laser for use in pump-probe experiments as well as a means for selecting single picosecond pulses from the free electron laser. One method of doing this involves using a photocathode electron gun.
The current research and development directed toward the production of a compact free electron laser that could be purchased and operated by a single academic department or individual investigator should be continued.
The region of the near infrared, visible, and ultraviolet accessible with commercial lasers covers wavelengths from roughly 10 µm to 200 nm. Noncommercial instrumentation can extend the limits of commercial laboratory lasers with some difficulty to 20 µm to 100 nm. This region is crucial for scientific research and is of great importance for much current and planned research, not only because photon sources and detectors are highly developed in this region, but also because of the fundamental properties of matter. The fingerprint region of molecular vibrations falls in the near infrared, valence transitions of chemical bonds fall in the visible and ultraviolet, and band gaps of solids fall in the visible or near infrared.
A wide variety of laboratory laser sources and nonlinear techniques based on laboratory lasers are effective in this region. These lasers are already widely tunable and capable of producing short pulses with high peak and average powers. Research and development will lead to further improvement. There are also existing free electron lasers that operate in this region, but conventional laboratory lasers will probably remain the mainstay of scientific research in this wavelength region. The national expenditure in 1993 on laboratory lasers used in scientific research was approximately $37M.
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.