Superprism phenomena in waveguide-coupled woodpile structures fabricated by two-photon polymerization

Here we give theoretical as well as experimental evidence for wavelength dependent super-refraction phenomena in waveguide coupled superprisms based on polymer woodpile structures. The photonic crystals were fabricated by means of the two-photon polymerization technique and have a partial band gap at near infrared wavelengths. To visualize the superprism effect the light propagating inside the woodpile structure was imaged using a CCD for a continuous range of wavelengths slightly above the band gap frequency. We were able to demonstrate a change of propagation direction from +50° (positive refraction) to -10° (negative refraction) with respect to the crystal surface normal for a wavelength range between 860 nm and 960 nm. Our results show the great potential of these low refractive index three-dimensional crystals, fabricated in a very fast and single-step process, to serve directly as functional micro-optical devices in the near infrared wavelength regime.