Dip-in depletion optical lithography of three-dimensional chiral polarizers.

We combine the concepts of dip-in and stimulated-emission-depletion-inspired optical lithography for the first time to fabricate three-dimensional (3D) nanostructures for photonics. For depletion of the photoinitiator ITX we employ a fiber-coupled laser diode at 639 nm wavelength. To demonstrate the performance of the experimental setup, we have fabricated 3D chiral layer-by-layer twisted woodpile structures with a lattice constant reduced by more than a factor of 2 compared to earlier results. The fabricated chiral photonic crystals serve as dual-band polarizers for circular polarization at visible and telecom wavelengths. Spectroscopic measurements agree well with scattering-matrix calculations.