Interplay of resonant cavity modes with localized surface plasmons: optical absorption properties of Bragg stacks integrating gold nanoparticles.

The optical properties of gold nanoparticles were modulated through integration in one dimensional photonic crystals made of silica and titania nanoparticles. Silica coated gold colloids were used to create a controlled optical defect buried within a periodic multilayer. Matching of the cavity mode with different spectral regions of the localized surface plasmon resonance yields a fine control over the effective absorption of the ensemble. This was achieved by varying the structural parameters of the multilayer. We also demonstrate that subtle environmental changes have dramatic effects on the optical absorption properties of the ensemble. Our work experimentally demonstrates that designed photonic structures can be used to spectrally tune the absorption peak characteristic of metal colloids.