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

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Nanotechnology

Background:

• Superprism phenomena, where small wavelength changes cause large angular deviations in light propagation, are crucial for optical devices.
• Photonic crystals offer unique light manipulation capabilities due to their periodic structures and band gaps.
• Polymer-based photonic crystals fabricated via two-photon polymerization present a versatile platform for micro-optics.

Purpose of the Study:

• To experimentally demonstrate and theoretically support wavelength-dependent super-refraction in waveguide-coupled polymer woodpile photonic crystals.
• To investigate the tunable refractive properties of these structures in the near-infrared spectrum.
• To assess the potential of these fabricated crystals as functional micro-optical devices.

Main Methods:

• Fabrication of polymer woodpile photonic crystals using the two-photon polymerization technique.
• Characterization of the partial band gap at near-infrared wavelengths.
• Imaging of light propagation within the woodpile structure using a CCD camera across a continuous wavelength range.

Main Results:

• Demonstrated a significant superprism effect with a tunable propagation direction change from +50° (positive refraction) to -10° (negative refraction).
• Observed this tunable refraction over a specific wavelength range of 860 nm to 960 nm, just above the band gap frequency.
• Confirmed the effectiveness of the polymer woodpile structure for controlling light propagation direction based on wavelength.

Conclusions:

• The study provides theoretical and experimental evidence for super-refraction in polymer woodpile photonic crystals.
• These low refractive index, 3D photonic crystals are fabricated rapidly and in a single step.
• The results highlight their potential for direct integration as functional micro-optical devices in the near-infrared regime.