Fabrication of a periodic structure with a high refractive-index difference by femtosecond laser pulses.

A microfabrication process using ultrafast laser pulses in glass was investigated. We investigated the formation of semiconductors by the irradiation of glasses with femtosecond laser pulses. ZnS- or PbS-doped SiO(2)-Al2O(3)-B(2)O(3)-CaO-ZnO-Na(2)O-K(2)O glasses were prepared by a melting method and irradiated by femtosecond laser pulses. Periodic structures in the sample glasses with a high refractive index difference were produced by femtosecond laser pulses. The maximum relative refractive index difference between the irradiated area and the nonirradiated areas was 20%. Diffraction gratings were also fabricated inside the ZnS- or PbS-doped silicate glasses. The diffraction efficiency of these gratings was approximately 90% in the infrared region.