Light-controlled erasure of induced χ(2) in thermally poled glasses

We demonstrate that the induced second order nonlinearity χ(2) generated in thermal poled doped borosilicate glasses can be erased by a prolonged exposure to near IR laser radiation. The evolution of the second harmonic signal with respect to laser time exposure, intensity and wavelength is reported. The IR laser radiation induced relaxation of the χ(2) is mainly related to two-photon absorption of the glass. The nonexponential time dependence of the second harmonic signal agrees with a simple model involving diffusion of photoexcited carriers. The reversible erasure process is also observed when the sample is exposed to near ultraviolet laser radiation.