Advanced Optical Materials

A simple method for the inscription of identical 20–30 nm features into single nanoparticles and their arrays is developed. Arrays of nanoparticles with exactly same optical properties can be used in nano-trapping including self-induced back-action trapping, Raman sensing, and metamaterial engineering.

Surface plasmon resonance (SPR) is excited on transparent oxide semiconductors “In₂O₃: Sn” in the near infrared range. Coupling between excitations of surface plasmons and molecular vibrations are demonstrated. The detection sensitivity of oxide-based SPR is close to that of gold-based SPR working in the visible range. These studies evidence the useful potential of oxide-based SPR in the NIR range for sensing applications.

Ultrasmall couplers for the excitation of plasmonic structures by photonic modes are presented. They are constructed by assembling point-like resonators in the near-field zone of the target structure. As a demonstration of its efficacy, this scheme is applied to unidirectional excitation of plasmonic waveguides. The overall footprint of the resulting coupling structures is less than λ²/10.

A graded-index anti-reflection coating with high optical transmittance, a rapid anti-fogging capability, and excellent robustness is fabricated via the stacking of Si-containing block copolymers and simple oxidation. The porosity in the nanostructured silica layers can easily be controlled by changing the fraction of the Si-containing block in the block copolymers. The high optical transparency can be maintained in harsh chemical, mechanical, and thermal environments, suggesting that the coating will be especially advantageous for outdoor applications.

Large-scale color changes (100s of nm) in polymer-stabilized cholesteric liquid crystals with a negative dielectric anisotropy are presented. Reflection peak tuning is enabled with DC electric fields through a unique peak splitting behavior. This simple approach can be applied in a variety of photonic applications.