The second-order optical nonlinearity of poled Ge25Sb10S65 chalcogenide glass was found to be 40–50% larger after femtosecond laser irradiation. The highest χ(2) was 11.4 pm/V. Raman spectral change indicated that centrosymmetric defects were created by fs light. These defects promoted the third-order optical nonlinearity of the glass and as a result, its second-order nonlinearity was also enhanced. The study shows that fs laser modification is an effective method of increasing the optical nonlinearity of photonic materials.
Vol. 282, no. 10 (May 2009), pp. 2081-2084