Radiation-induced effects in a new class of optical waveguides: the air-guiding photonic crystal fibers

Transient radiation-induced effects in air-guiding photonic crystal fibers (Air-PCF) are investigated for the first time to our knowledge. We characterize the vulnerability of this kind of waveguide by measuring the time dependent changes of their radiation-induced attenuation (RIA) at 1.55 [micro]m. We compare their radiation response to those of two silica-based single-mode fibers with germanium-doped and pure-silica cores. An X-ray pulse induces globally the same effects in all waveguides: a strong and transient increase of RIA. For higher tested doses (10 < D < 100 Gy), Air-PCF exhibits an interesting saturation of RIA at ~0.1 dB/m. The possible mechanisms involved in this radiation response are discussed. In particular, we assume that the design of the photonic bandgap structure of the fiber, responsible for the light guidance in the air-core, could strongly affect the amplitude of RIA. The kinetics of RIA recovery depends predominantly on the point defects created at the air/silica interface and in the silica-based part of the microstructured cladding. Index Terms--Color centers, photonic crystal fibers, pulsed X-rays, radiation effects.