Fabrication of three-dimensional periodic microstructures in photoresist SU-8 by phase-controlled holographic lithography

Three-dimensional (3D) periodic dielectric structures were recorded in a commercial photoresist SU-8 by exposure to intensity patterns created by five interfering coherent femtosecond Ti: sapphire laser pulses. Periodic symmetry of these patterns was controlled by the choice of mutual convergence angles of the beams as well as their phases. The fabricated structures are mechanically and chemically stable, well-connected frameworks of SU-8 regions in air; the smallest dimensions of SU-8 features are in the sub-micrometre range. The structures exhibit a high degree of long-range order across areas as large as 1 mm in cross-section.