METHOD AND DEVICE FOR FORMATION OF DIFFRACTION GRATING

摘要

PROBLEM TO BE SOLVED: To form a diffraction grating in an optical fiber by including a process of positioning ultrashort laser pulses to cross each other and of forming an interference pattern in a material so that the interference pattern causes the corresponding periodical changes from a first refractive index of the material. SOLUTION: A laser 102 generates ultrashort laser pulses 104 which enter a converging lens 106. The converging lens 106 converges the ultrashort laser pulses 104 to produce converged ultrashort laser pulses 108 which enters a diffraction optical member 110. The first and second ultrashort laser pulses 202, 204 generated by the diffraction optical member 110 cross in a region 206. The interference pattern formed in the region 206 corresponds to the periodical laser intensity in the crossing region 206, and the periodical laser intensity causes corresponding periodical changes in the refractive index of the core and cladding.