Optical colouring and surface chemistry of ultrafast laser generated debris on polycarbonate

Laser alteration of polymers is an important field which has received a great deal of attention related to altering the surface and bulk of cheap commonly used plastics to generate useful effects. Of these materials polycarbonate is one of the most commonly used thermoplastic materials available on the market and much attention has gone into understanding and adapting it for a variety of applications. These include altering wettability, creating waveguides or microfluidic channels and graphitized circuitry. However, the optical performance and control of the far field response have received less attention, yet interest in laser-coloured plastics and polymers for applications such as ID cards and customized engraving of components is well-motivated. Here we explore the effects of several laser parameters on the structuring of polycarbonate for tailored optical responses and investigate the resulting texturing, specifically, the formation and redeposition of debris, the surface morphology and chemistry, and how these factors interact to generate a variety of colours.