Three dimensional waveguide fabrication in PMMA using femtosecond laser micromachining system

Femtosecond lasers have been widely used for the micro structuring of transparent materials for a wide range of applications. The local change in refractive index by the irradiation of laser pulse has been exploited for optical applications ranging from optical data storage to the fabrication of waveguides and couplers. In this work, a Ti:Sapphire femtosecond laser (800nm, ~150 fs and 1 kHz) is used for the fabrication of three dimensional (3D) waveguides in thick PMMA substrates. The femtosecond laser microfabrication (FLM) system consists of the laser and three translational (X, Y and Z) stages and one rotational controlled motorized stages. The coordinated motion of these four stages can be used to generate desired three dimensional pattern inside the transparent material due to refractive index modification. This work will present the design of 3D waveguide using commercially available solid modeler, the generation of motion control codes using a customized post processor and the writing of the developed pattern. Also, control of the laser process parameters to obtain desired feature quality by minimizing self-focusing and self-trapping in PMMA is discussed. This FLM system along with the 4-axis machining capability can be effectively used for the fabrication of complex 3D waveguide circuits in a single step process.