Hollow silica, metal, and plastic waveguides for hard-tissue medical applications

A new type of flexible hollow waveguide made of polyimide was developed. Mechanical bending and flexibility of the polyimide was changed and brought to be similar to that of Teflon hollow waveguide using a plastic sleeve. The optical characteristics of this new waveguide were studied and it was shown that high power (up to 25) Watts of carbon-dioxide laser radiation can be delivered. The delivered power remained constant for more than 150 seconds, which shows that the polyimide waveguides may be suitable for applications in medicine, where the requested maximum delivered power is about 20 Watts. Transmission (T) as a function of bending (1/R), where R is the radius of curvature, has shown that very strong bending may be obtained (R greater than or equal to 4 mm) without damage to the waveguide. Also demonstrated was the importance of angle, in addition to the radius of bending. The measurements of divergence of delivered beam was small (approximately 10^-3), which is comparable with those obtained for core fibers. Beam profile measurements have shown that the shape and mode distribution of the delivered radiation from waveguide are similar to that delivered by the coupled carbon-dioxide radiation. The measured value of maximum accepted incident angle of the beam on the internal wall of the waveguide was about 12 degrees which is larger than of silica and Teflon waveguides.