Glasses are important materials for novel technologies, as their properties can be tailored by doping and compositional changes. Furthermore, glasses can also be microstructured, making them interesting for optical and photonic applications. Corning Gorilla Glass is an alkali aluminosilicate glass commonly used as protective layer in smart phones and tablets thanks to its outstanding mechanical properties. Recently, it has been demonstrated the use of femtosecond direct laser writing of waveguides in Gorilla Glass, prompting it for integrated photonic/electronic devices. Therefore, it is important to study the nonlinear optical properties of Gorilla Glass as well as their laser-inscribed waveguides, since the effects of the laser writing process on the nonlinearity are not totally understood.
Here we investigate the third-order nonlinear optical properties of waveguides fs-pulses written waveguides in Gorilla Glass, by using the Dispersive-scan (D-scan) method. The nonlinear refractive index measured in the waveguide is lower than the one for the pristine material and its value depends on the writing pulse energy. For waveguides fabricated with pulse energy of 250 nJ, for instance, n2 is about three times lower than the one for the pristine sample. Micro Raman measurements were performed in the microstructured material in order to better understand the mechanisms of laser modification. Raman spectroscopy revealed the reduction and broadening of the high-frequency band related to non-bridging oxygens, which can explain the decrease of n2. Therefore, our results not only show the potential of using D-scan for waveguides nonlinear characterization, but also demonstrate and interpret the decrease of the nonlinear index of refraction in fs-laser micromachined waveguides in Gorilla Glass, which potential implications for photonic devices.