Advanced Optical Materials Issue 1

The internal architecture of metal-dielectric Au/Co/Au–SiO₂magnetoplasmonic nanodisks provides control over the internal electromagnetic field distribu on by varying the relative contributions of the magneto-optically active layers and the optically lossy layers. This allows simultaneous tuning of the magneto-optical activity and the absorption. On page OP36, A. Cebollada and co-workers show how placing the dielectric between the upper Au layer and the Co produces a configuration of sizeable magneto-optical activity and low optical loss. If the dielectric is placed below the Co, the magneto-optical activity is maintained, but the optical losses are larger.

M. S. Schmidt et al. describe on page OP11 a simple, two-step fabrication process to as-semble flexible, freestanding nanopillars into large-area substrates. These substrates can be made using readily available silicon-processing equipment and are suitable for SERS, having a large, uniform Raman enhancement.

Using a simple two step fabrication process substrates with a large and uniform Raman enhancement, based on flexible free standing nanopillars can be manufactured over large areas using readily available silicon processing equipment.

Modal gain per unit length versus launched pump power is predicted and measured in a 47.5 at.% Yb³⁺-doped potassium double tungstate channel waveguide. The highest measured gain exceeds values previously reported for rare-earth-ion-doped materials by two orders of magnitude.

Optical metamaterials have unusual optical characteristics that arise from their periodic nanostructure. Their manufacture requires the assembly of 3D architectures with structure control on the 10-nm length scale. Such a 3D optical metamaterial, based on the replication of a self-assembled block copolymer into gold, is demonstrated. The resulting gold replica has a feature size that is two orders of magnitude smaller than the wavelength of visible light. Its optical signature reveals an archetypal Pendry wire metamaterial with linear and circular dichroism.

When a droplet hits the surface of water, it is often observed that a water column, or ‘back-jet’, surges upwards. Counterintuitive though it might be, a similar phenomenon can occur when ultrafast light pulses shine on a nanostructured metal surface. These sub-wavelength ‘nanojets’ occur in the regions of highest local field enhancements. For more details, see the article by V. K. Valev et al. on page OP29.

In response to the incident light’s electric field, the electron density oscillates in the plasmonic hotspots producing an electric current. Associated Ohmic losses raise the temperature of the material within the plasmonic hotspot above the melting point. A nanojet and nanosphere ejection can then be observed precisely from the plasmonic hotspots.

On page OP49, M.-H. Jo and co-workers describe a method of control over photocurrent detection by manipulating ferroelectric domain configurations. The magnitude
is spectrally centered around charged domain walls that are associated with oxygen vacancy migration in BiFeO₃, where potential gradients caused by spontaneous polarization yield asymmetric and nonlinear photocarrier dynamics.

Potential gradients due to the spontaneous polarization of BiFeO₃ yield asymmetric and nonlinear photocarrier dynamics. Photocurrent direction is determined by local ferroelectric domain orientation, whereas magnitude is spectrally centered around charged domain walls that are associated with oxygen vacancy migration. Photodetection can be electrically controlled by manipulating ferroelectric domain configurations.

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.

Hemispherical microresonators with tunable sizes are obtained based on the hydrophobic effect on distributed Bragg reflectors. Under optical excitation, whispering gallery mode lasing is observed from the dye-doped microresonators at room temperature. The results indicate the potential application of the flexible microresonators in photonic integrated circuits.

To identify the depletion mechanism in the stimulated-emission-depletion (STED) inspired photoresist composed of a ketocoumarin photoinitiator in pentaerythritol tetraacrylate, we perform lithography with pulsed excitation and tunable delayed depletion. A fast component can unambiguously be assigned to stimulated emission. Our results allow the systematical optimization of the conditions in next-generation STED direct-laser-writing optical lithography.

Plasmonic graphene has been fabricated by G. Xu et al. using thermally assisted self-assembly of Ag nanoparticles on graphene. The localized surface-plasmonic effect is demonstrated with the resonance frequency shifting from 446 to 495 nm when the lateral dimension of the Ag nanoparticles increases from about 50 to 150 nm. Both the resonance frequency and amplitude decrease with increasing graphene thickness. In addition, plasmonic graphene shows much improved electrical conductance by a factor of 2–4 as compared to the original graphene.

Plasmonic graphene is fabricated using thermally assisted self-assembly of silver nanoparticles on graphene. Tuning of the surface plasmonic resonance frequency and amplitude in plasmonic graphene is demonstrated.

Leaf minerals function as internal l

ight scatterers inside leaves. They transfer light from the saturated upper tissue into the light deprived lower tissue. This eases the steep light gradient inside the leaf and improves photosynthetic efficiency on the tissue scale.