Fabrication Of1D,2D And3D Polymer-based Periodic Structures By Mass Transport Effect

We have theoretically and experimentally investigated the formation of both active and passive surface relief gratings on two kinds of photosensitive polymers:negative photoresist and azobenzene copolymer. The common mechanism of the structures formation was attributed to mass transport effect, which however pushes the materials in opposite directions in these two materials. The fabrication technique is based on the use of interference lithography, which allowed to create large and uniform-structures.In the first case,1D and2D passive periodic surface relief structures were created on the negative photoresist SU8thanks to the shrinkage effect during the crosslinking process. In the second case,1D,2D and3D active periodic structures have been obtained thanks to the movement of DR1/PMMA copolymer materials from regions of high intensity to those of low intensity irradiation. The modulation amplitude of structures is optimized by controlling the film thickness, the structure periodicity, the exposure dosage, and the polarizations of interference laser beams.Applications of these structures for multiple wavelength DFB laser, nonlinear photonic crystals, and waveguide coupling have been discussed.