Three-Dimensional Nanostructures for Photonics

Recent progress in direct laser writing of three‐dimensional (3D) polymer nanostructures for photonics is reviewed. This technology has reached a level of maturity at which it can be considered as the 3D analogue of planar electron‐beam lithography. Combined with atomic‐layer deposition and/or chemical‐vapor deposition of dielectrics—the 3D analogues of planar evaporation technologies, the 3D polymer templates can be converted or inverted into 3D high‐refractive‐index‐contrast nanostructures. Examples discussed in this review include positive and inverse 3D silicon‐based woodpile photonic crystals possessing complete photonic bandgaps, novel optical resonator designs within these structures, 3D chiral photonic crystals for polarization‐state manipulation, and 3D icosahedral photonic quasicrystals. The latter represent a particularly complex 3D nanostructure. Direct laser writing of 3D nanostructures for photonics has reached a level of maturity at which it can be considered the 3D analogue of planar electron‐beam lithography. The recent progress in this field is reviewed, and examples for silicon‐based woodpile photonic crystals, novel optical resonator designs within these structures, 3D chiral photonic crystals, and 3D icosahedral photonic quasicrystals are demonstrated.