Laser Sources

Since the construction of the first laser based on ruby, widely ranging materials have been adopted as laser media, and the range is still continually being extended to provide output at new wavelengths: according to Charles H. Townes, one of the pioneers of laser development, ‘almost anything works if you hit it hard enough’. As can be seen from a glance at Appendix 1, output from commercial lasers now covers most of the electromagnetic spectrum through from the microwave region to the ultraviolet, and much effort is being concentrated on extending this range to still shorter wavelengths. Amongst a host of tantalising possibilities is the prospect of obtaining holograms of molecules by use of an X-ray laser, for example.