Optical nonlinearity in gamma-ray-irradiated lead-silicate glass

Gamma-ray-irradiated lead-silicate glass shows enhanced photoinduced quasi-phase-matched second-harmonic generation. This is due to the formation of color centers, which serve as traps for space charge, resulting in an internal dc field due to the coherent photovoltaic effect. The color center formation also enhances the χ⁽³⁾ nonlinearity, which contributes to the photoinduced quasi-phase-matched second-harmonic generation as well. We separate these two contributions and show their respective roles.