3D Direct Laser Writing without Femtosecond Lasers

Direct laser writing is a common technique for generating 3-dimensional (3D) refractive index modification in materials. It relies on a two-photon absorption mechanism and to date requires high-power femtosecond lasers. We demonstrate a method that uses a low-power quasi-CW laser to write 3D, sub-wavelength features in a transparent material. To achieve this, we exploit the time-dependent changes in the linear absorption coefficient of the material to generate a localized modification of the refractive index, up to 12%. We present an analytical model for material modification, simulation results, and experimental results, as well as a technique for in-situ characterization of the material modification.