Hollow single-crystal sapphire fibers have been used to deliver CO2, laser energy for applications involving cutting, welding, and laser surgery. The hollow sapphire fibers are 125-cm long and range in inner diameter from 250 to 1050 μm. The principle of operation of these fibers is based on the index of refraction n being less than 1 at 10.6 μm. With a n < 1 cladding inner layer and an air core, the hollow waveguide functions like a fiber. This structure is unlike the leaky, hollow metal waveguides in which significant mode mixing can result from bending the waveguides. In contrast, the sapphire fibers are single mode.
© 1991 Optical Society of AmericaPDF Article