Absorptive structures fabricated by laser writing

The spectral properties of metallic surfaces are of much interest in applications such as solar absorption. These may help improve the performance of solar thermal systems and solar cells. The fabrication of periodic metallic features on the device surface is known to increase absorption and the use of diffractive structures has been reported. In this paper we report use of corrugated metal structures formed by a novel approach. Two photon polymerisation is used to write a 2D grid pattern, with a pitch of either 2 or 3 microns, onto which a chrome metal layer was evaporated. A Ti:sapphire laser, with wavelength 795 nm, 80MHz repetition rate, 100 fs pulse duration and an average power of 700 mW, was used to write the grid in a Zr-loaded sol-gel. The measured reflection and transmission properties show that the absorption increases in a part of the spectrum that can be related to the structure's dimensions. A RCWA code was used to define the optimal parameters for solar absorption in this system.