SINGLE-EXCIMER-PULSE WRITING OF FIBER GRATINGS BY USE OF A ZERO-ORDERNULLED PHASE MASK - GRATING SPECTRAL RESPONSE AND VISUALIZATION OF INDEX PERTURBATIONS

Optical fiber Bragg reflectors have been written by irradiating the fi ber from the side through a phase mask with a single pulse of high-pow er 249-nm excimer-laser light. Efficient tapping of light to the radia tion modes has been achieved for light at wavelengths shorter than the Bragg wavelength. The photoinduced periodic refractive-index perturba tions have been observed directly with an optical microscope and are s hown to have the same period as the phase mask and to be highly locali zed on one side, the irradiated side of the fiber core-cladding bounda ry.