Delivery of coherent radiation from terahertz to X-rays

The use of hollow glass waveguides (reflectively coated or uncoated) in combination with simple, inexpensive hollow linear tapers as a replacement for lenses enables the construction of a delivery system that can be used for radiation from terahertz to x-rays. The simplicity of the hollow taper as a replacement for a lens has numerous practical advantages for handling radiation outside the near infrared-visible region. Hollow tapers using grazing-incidence reflection can concentrate the radiation like a lens, but have no reflective Fresnel surface losses. In addition, both the point of highest intensity and its area are known and fixed in space. The power density is easily measured. When used as a focusing lens for material irradiation, the precise power density is uniform and can be delivered to a precise location. These simple waveguide elements already show promise for delivery of a spectrum of radiation from terahertz to x-rays. They work very well especially with collimated sources where grazing incidence reflection keeps the throughput high. As coherent x-ray lasers become a reality, better transmission will result enabling a wide spectrum of applications especially in medicine.