High power laser delivery using anti-resonant hollow core fiber

Currently, the power handling capability of optical fibers is primarily limited by glass damage thresholds and induced nonlinearities, including stimulated Brillouin scattering and stimulated Raman scattering. In order to mitigate unwanted nonlinear effects, a majority of high power delivery fibers have increased core sizes, which are generally used near the threshold of multimode operation. Under high power, thermal changes lead to transverse mode instabilities which degrade the overall beam quality. We have been investigating hollow core fibers based on the anti-resonant effect (ARHCF) due to their excellent guiding properties, such as low loss, large core sizes, wide transmission windows, and significantly increased optical nonlinearity and damage thresholds. Anti-resonant HCFs have significantly simpler designs compared to other microstructured fibers, namely photonic bandgap fibers, which leads to more flexibility and less complex fabrication. An ARHCF design was optimized in Comsol Multiphysics for single mode operation, low propagation loss, and low bending loss. The ARHCF was fabricated at the University of Central Florida. Initial testing has shown that power handling up to 170 W input, 0.7 GW/cm² at the fiber facet is possible with no damage to the fiber.