Writing waveguides in glass with a femtosecond laser

TLDR

The study aimed to enable telecom optical devices by investigating 810‑nm femtosecond laser effects on various glasses. Using a microscope objective to focus 810‑nm femtosecond pulses, the authors wrote transparent yet visible round‑elliptical damage lines in high‑silica, borate, soda‑lime silicate, and fluorozirconate glasses. Measurements revealed a 0.01–0.035 refractive‑index increase and various defect centers, indicating multiphoton interactions and the feasibility of writing 3‑D optical circuits in bulk glasses.

Abstract

With the goal of being able to create optical devices for the telecommunications industry, we investigated the effects of 810-nm, femtosecond laser radiation on various glasses. By focusing the laser beam through a microscope objective, we successfully wrote transparent, but visible, round-elliptical damage lines inside high-silica, borate, soda lime silicate, and fluorozirconate (ZBLAN) bulk glasses. Microellipsometer measurements of the damaged region in the pure and Ge-doped silica glasses showed a 0.01–0.035 refractive-index increase, depending on the radiation dose. The formation of several defects, including Si E′ or Ge E′ centers, nonbridging oxygen hole centers, and peroxy radicals, was also detected. These results suggest that multiphoton interactions occur in the glasses and that it may be possible to write three-dimensional optical circuits in bulk glasses with such a focused laser beam technique.