COMPARISON OF ONE-PHOTON AND 2-PHOTON EFFECTS IN THE PHOTOSENSITIVITYOF GERMANIUM-DOPED SILICA OPTICAL FIBERS EXPOSED TO INTENSE ARF EXCIMER-LASER PULSES

The growth rate of fiber Bragg gratings written using 193 nm light fro m an ArF excimer laser is linearly proportional to the laser pulse ene rgy density for fibers with high germanium doping but proportional to the square of the pulse energy density for standard telecommunications fibers with low germanium concentration. The two-photon process in st andard fibers yields refractive index increases that saturate around 1 0(-3), an order of magnitude improvement over previous results in this type of fiber without sensitization treatment. The two types of photo induced refractive index gratings have comparable thermal stability an d preserve about 50% of their initial magnitude after 30 min at 600 de grees C. (C) 1995 American Institute of Physics.