Tailoring of photonic structures by femtosecond laser lithography

摘要

Micro and nano structuring of materials using femtosecond lasers has attracted considerable interest as a tool for fabrication of various photonic devices, such as diffractive elements, photonic crystals (PhC), optical waveguides, etc. Direct Laser Write (DLW) technique based on 3D high-resolution drawing of refractive index modulation structures is especially attractive, since it allows fabrication of 3D photonic micro- and nano-structures without the tediousness of planar microfabrication techniques borrowed from semiconductor industry (e.g., electron-beam lithography, thin film deposition, dry-etching, etc.). Here, we describe application of femtosecond DLW lithography for the fabrication of 3D PhC structures in photoresists and describe application of these structures for collimation of optical beams. Using theoretical analysis and numerical simulations we show that 3D woodpile architecture PhC enables collimation of divergent optical beams via negative diffraction in a 3D periodic structure. Using parameters of 3D woodpile structure obtained from the theoretical analysis, woodpile structures were fabricated by DLW technique and beam collimation in these structures was demonstrated experimentally.