Formation of pores in the optical fiber exposed to intense pulsed UV radiation

Abstract

A new method of forming refractive index gratings (type-IIA Bragg gratings) in the optical fiber by exposing it to intense UF laser radiation is suggested. Central in this method is the generation and propagation of micropores in the parts of the fiber where mechanical stresses are localized. It is shown that such parts are the center of the core and the core-cladding interface. The temperature of the radiation-heated germaniumdoped core is found experimentally and theoretically. Thermal stresses arising in the heated fiber are calculated. A theory of cracking and pore formation in the fiber exposed to intense laser pulses is worked out. The pore size distribution, pore formation and growth rate, and pore density versus time of laser action are estimated.