Fabrication of strong long-period gratings in hydrogen-free fibers with 157-nm F_2-laser radiation

Long-period gratings were fabricated in standard telecommunication fiber (Corning SMF-28) by use of what is believed to be record short-wavelength light from a 157-nm ${\mathrm{F}}_2$ laser. Strong loss peaks were formed without the need for enhancement techniques such as hydrogen loading. The magnitude of the attenuation peak was sensitive to the single-pulse laser fluence, decreasing with increasing pulse fluence as a result of nonuniform 157-nm laser interaction with both the fiber cladding and core. The long-period fiber gratings have good wavelength stability $\left(\mathrm{\Delta }\lambda \sim 7 \mathrm{nm}\right)$ under thermal annealing at 150 °C.