Spiral-type terahertz antennas and the manifestation of the Mushiake principle.

We report on the experimental and theoretical study of the resonant eigenmodes of spiral-type terahertz antennas. The analysis is carried out for a varying number of spiral windings. For larger numbers the structure possesses a self-complementary property which allows the application of the Mushiake principle predicting that the impedance of such structures is half the impedance of free space.

Optical resonances of bowtie slot antennas and their geometry and material dependence.

In order to provide a guide for the design and optimization of bowtie slot antennas in the visible and near infrared spectral regime, their optical properties have been investigated with emphasis on geometry and materials. Although primarily theoretical, experimental investigations for reduced thickness cases are also included. As characterized by their field patterns, two types of resonances are discussed: plasmonic and Fabry-Pérot-like resonances.

Thermal lensing in an end-pumped Yb:KGW slab laser with high power single emitter diodes.

We demonstrate that it is possible to pump an Ng-cut Yb:KGW crystal slab with up to 18W by a single emitter laser diode and still achieve a nearly diffraction limited output beam with a M(2) value below M(2) < 1.1 and optical to optical efficiencies of more than 44%. Furthermore, we have measured the focal length of thermally induced lenses in an Yb:KGW crystal slab which was end-pumped by 12 W and 18 W single-emitter diodes.

Resonances in complementary metamaterials and nanoapertures.

We theoretically analyze the properties of metamaterials which have been designed by taking advantage of Babinet's principle. It is shown that the complementary structure exhibits both a complementary spectral response and field distribution of the respective eigenmodes. For complementary split-ring resonators, we show that the spectral resonance features can be explained from two different perspectives.

Resonance hybridization in double split-ring resonator metamaterials.

We introduce a plasmon hybridization picture to understand the optical properties of double split-ring resonator metamaterials. The analysis is based on the calculated reflectance spectra from a finite-integration time-domain algorithm. Field distributions of the double split-ring resonators at the resonant frequencies confirm the results from the plasmon hybridization analysis.