Abstract

The low-concentration of fused silica matrix in intrinsic defect sites, results in a high transmission extending down to short wavelengths and in a low-yield photosensitivity processing, rendering the generation of refractive index and structural modifications in that glass difficult, using nanosecond ultraviolet laser sources [1]. For improving the photosensitivity of pristine silicate glass, high pressure hydrogenation is employed prior to exposure, for reducing irradiation time and increasing refractive index changes obtained. Alternatively, the use of femtosecond laser sources is an efficient approach in inscribing Bragg reflectors in all-silica fibres, without employing pre-conditioning steps. The inscription of Bragg reflectors in undoped silicate fibres has been presented before, employing mainly infrared laser sources [2]. However, the use of shorter wavelengths such as 267nm femtosecond radiation for such index engineering, was proved not to be a high-yield approach, needing large accumulated doses and being inefficient for the case of non-hydrogenated species [3]. The photosensitivity and Bragg grating inscription in all-silica standard and microstructured optical fibres utilising 248nm, 5ps and 500fs laser radiation are presented herein. The all-silica fibers exposed, were the fluorine depressed cladding Z-fiber, fabricated by Sumitomo, the micro-structured, endlessly single-mode fibres ESM-12-01, fabricated by former Blazephotonics and the LMA-10 fabricated by Crystal Fiber.

© 2009 IEEE