Abstract: The invention relates to a process for inscribing a three-dimensional structure formed from variations in refractive index in the bulk of a transparent oxide glass comprising silver ions by femtosecond-laser-beam irradiation, the method comprising: generating a laser beam made up of a series of ultra-brief light pulses of pulse duration shorter than the characteristic time of thermalization of the glass so as to achieve an excitation at the point of irradiation via multi-photon interaction; focusing said beam at a desired depth in the glass; irradiating point by point the glass with said beam so as to form the structure in the glass along a predetermined path, the number of pulses, the repetition rate of the pulses and the irradiance at each irradiation point being controlled to induce an accumulation of silver aggregates localised in an annular peripheral region around an irradiation point, said accumulation of aggregates generating a variation in refractive index in the annular peripheral region around the

Abstract: Optical fiber (1) made of a photosensitive glass and with a rectangular cross section, wherein the radius of curvature of a corner of the rectangular cross section is smaller than 100 microns.

Abstract: Optical fiber (1) made of a photosensitive glass and with a rectangular cross section, wherein the radius of curvature of a corner of the rectangular cross section is smaller than 100 microns.