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Stefan Mendach

Publications and source records attributed to Stefan Mendach.

6 recordsLinked to original sources
arXiv2017

Tunable Plasmonic Nanoantennas in Rolled-up Microtubes Coupled to Integrated Quantum Wells

We propose and realize a tunable plasmonic nanoantenna design consisting of two stacked Ag cuboids that are integrated into a rolled-up semiconductor microtube. The antenna's resonance is tuned by varying the cuboid's distance to match the photoluminescence emission of an embedded GaAs quantum well. Spatially, spectrally and temporally resolved photoluminescence measurements reveal a redshift and a reduction in lifetime of the quantum-well emission as signatures for the coupling to the antenna system. By means of finite-element electromagnetic simulations, we assign the coupling to an excitation of a high-order plasmonic mode inside the Ag cuboids.

physics.optics↗
arXiv2011

Transmission enhancement in three-dimensional rolled-up plasmonic metamaterials containing optically active quantum wells

We investigate three-dimensional rolled-up metamaterials containing optically active quantum wells and metal gratings supporting surface plasmon polarition resonances. Finite-difference time-domain simulations show that by matching the surface plasmon polarition resonance with the active wavelength regime of the quantum well a strong transmission enhancement is observed when illuminating the sample with p-polarized radiation. This transmission enhancement is further increased by taking advantage of the Fabry-Perot resonances of the structure.

cond-mat.mtrl-sci↗
arXiv2011

Gain in Three-Dimensional Metamaterials utilizing Semiconductor Quantum Structures

We demonstrate gain in a three-dimensional metal/semiconductor metamaterial by the integration of optically active semiconductor quantum structures. The rolling-up of a metallic structure on top of strained semiconductor layers containing a quantum well allows us to achieve a three-dimensional superlattice consisting of alternating layers of lossy metallic and amplifying gain material. We show that the transmission through the superlattice can be enhanced by exciting the quantum well optically under both pulsed or continuous wave excitation. This points out that our structures can be used as a starting point for arbitrary three-dimensional metamaterials including gain.

physics.optics↗
arXiv2009

Spin-wave interference in three-dimensional rolled-up ferromagnetic microtubes

We have investigated spin-wave excitations in rolled-up Permalloy microtubes using microwave absorption spectroscopy. We find a series of quantized azimuthal modes which arise from the constructive interference of Damon-Eshbach type spin waves propagating around the circumference of the microtubes, forming a spin-wave resonator. The mode spectrum can be tailored by the tube's radius and number of rolled-up layers.

cond-mat.other↗
arXiv2009

Observation of spin-wave propagation in permalloy microstripes

We report on the propagation of spin waves in permalloy microstripes. By means of scanning Kerr microscopy combined with continuous microwave excitation, we detect the time evolution of spin-wave interference patterns in an external magnetic field. Assuming transverse spin-wave quantization we can directly measure the amplitude, phase velocity and damping for the corresponding transversal wave mode numbers m. We find that the spin-wave interference pattern is dominated by m=0 and m=2 with phase velocities v_0=71 km/s and v_2=47 km/s, respectively.

cond-mat.mes-hall↗