UV laser processing and multiphoton absorption processes in optical telecommunication fiber materials

Over the last two decades UV-induced Δ n profiling in SiO 2 glasses was widely used for production of in-fibre/waveguide Bragg grating-based (BG) optical devices for photonics industry. These devices have found numerous applications in optical fiber sensing, telecommunication and all fiber laser systems. From a practical point of view, it is the most important photo-induced phenomenon observed each time a silica glass is exposed to convenient low or high UV intensity laser light through one quantum and multi-photon mechanisms respectively. In fact, depending on the materials, conditions of exposure and conditioning processes (i.e. the photosensitization process), UV induced index changes may vary from 10−5 up to 10−2. In the following, for the purpose of illustrating the complexity of this multiple-variable dependence, we present a review of how factors such as exposure time, laser wavelength, sensitization process, pulse duration, or the chemical composition, can affect the photosensitive response of silica-based glasses, i.e. the number of photons involved in the initial step of absorption, the writing efficiency and so on.