Hollow Fiber Transmits CO2 Laser Radiation

Researchers at Massachusetts Institute of Technology in Cambridge have produced wavelength-scalable hollow optical fiber that can transmit enough of the output of a 25-W CO₂laser to burn holes in paper and PES film. Even with maximum laser power densities approaching 300 W/cm², there was no observable fiber damage as long as there was optimum coupling of the beam into the fiber core.

As described in the Dec. 12 issue of Nature, the scientists lined the fiber with an omnidirectional dielectric mirror and used multiple alternating submicron-thick layers of high-refractive-index glass and low-refractive-index polymer to produce the bandgap necessary for light confinement. By varying layer dimensions, they were able to change the fundamental and high-order transmission windows and thereby scale the transmission from 750 nm to 10.6 µm. Typical transmission losses were less than 1.0 dB/m.