Enhanced χ⁽³⁾ in γ-ray irradiated bulk glass

The non-linear coefficient χ⁽³⁾(ω, ω, 0, 2ω) of γ-ray irradiated (up to 1.7 Mrad) light-flint silicate bulk glass (Schott glass LF5) was measured. The process involves four wave mixing which produces the second harmonic (2ω) from a glass sample irradiated with the fundamental beam at ω while applying a DC electric field. A theoretical model which accounts for absorption at 2ω is developed and an experimental method is employed to determine the non-linear coefficients in the presence of phase mismatch. It is shown that the non-linearity is enhanced as a function of the gamma irradiation and the color centers formation.