Carsten Rockstuhl

Optical properties of mesogen-coated gold nanoparticles

In this work, the physical and optical properties of gold nanoparticles functionalized with laterally grafted nematic ligands were studied. In particular, the influence of the nanoparticle size on the mesomorphic behavior and optical properties of the composite was investigated. To obtain an in-plane alignment of the mesogens, thin oriented films were prepared by shearing and characterized by polarized absorption spectroscopy. While the sub-2nm nanoparticle thin film only showed birefringence due to a strong damping of the plasmon resonance, larger NPs exhibit a strong dichroism with a shift of the NP plasmon resonance by about 50 nm. These results demonstrate the possibility to obtain a bulk NP metamaterial with tunable plasmonic properties by chemical engineering of the NP ligands.

Liquid crystal plasmonic metamaterials

The electromagnetic response of metamaterial can be managed by combining resonances and interferences of different materials and on different lengths scales. In our contribution we study composite metamaterials containing resonant plasmonic metallic nanoparticles that show organization. The material bases its non-conventional properties on short distance self-organization by mesogens that form a liquid crystal material. We analyze the properties of such materials with a structural model containing organized nanoparticles. Theoretically insight of the electromagnetic properties is provided and we give details on their optical properties.

Semiconductor-based narrow-line and high-brilliance 193-nm laser system for industrial applications

We present a novel industrial-grade prototype version of a continuous-wave 193 nm laser system entirely based on solid state pump laser technology. Deep-ultraviolet emission is realized by frequency-quadrupling an amplified diode laser and up to 20 mW of optical power were generated using the nonlinear crystal KBBF. We demonstrate the lifetime of the laser system for different output power levels and environmental conditions. The high stability of our setup was proven in > 500 h measurements on a single spot, a crystal shifter multiplies the lifetime to match industrial requirements. This laser improves the relative intensity noise, brilliance, wall-plug efficiency and maintenance cost significantly. We discuss first lithographic experiments making use of this improvement in photon efficiency.

Front and rear side photonic nanostructures for an optimal photon management

We investigate the light trapping of various photonic nanostructures integrated into the front and rear side of silicon solar cells. Combinations of textured surfaces and amorphous photonic crystals enhance the absorption by more than 15%.

Optical Properties of Bottom‐up Metamaterials

The optical properties of metamaterials that can be fabricated with bottom‐up approaches and which rely on a suitable arrangement of metallic nanoparticles in space are discussed. We outline the numerical challenges that have to be solved in order to describe such structures efficiently, discuss possible means to assign effective properties to these metamaterials and reveal the possible material dispersion that can be achieved by exploiting various carefully selected geometries.

Randomly Textured Surfaces for Photon Management in Silicon Thin Film Solar Cells

Rigorous diffraction theory is used to reveal the peculiarities of randomly textured surfaces used for photon management. The effect of such surfaces in solar cells with an increasing complexity is analyzed to provide unprecedented insights.