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Utilizing Bragg surface plasmon polaritons (SPPs) on metal nanostructures for the use in optical devices has been intensively investigated in recent years. Here, we demonstrate the integration of nanostructured metal electrodes into an ITO-free thin film bulk heterojunction organic solar cell, by direct fabrication on a nanoimprinted substrate. The nanostructured device shows interesting optical and electrical behavior, depending on angle and polarization of incidence and the side of excitation. Remarkably, for incidence through the top electrode, a dependency on linear polarization and angle of incidence can be observed. We show that these peculiar characteristics can be attributed to the excitation of dispersive and non-dispersive Bragg SPPs on the metal&ndash, dielectric interface on the top electrode and compare it with incidence through the bottom electrode. Furthermore, the optical and electrical response can be controlled by the organic photoactive material, the nanostructures, the materials used for the electrodes and the epoxy encapsulation. Our device can be used as a detector, which generates a direct electrical readout and therefore enables the measuring of the angle of incidence of up to 60&deg, or the linear polarization state of light, in a spectral region, which is determined by the active material. Our results could furthermore lead to novel organic Bragg SPP-based sensor for a number of applications.

The performance of organic light-emitting diodes (OLEDs) is boosted by adding star-shaped plasmonic particles, so called nanostars. For this purpose, silver-enhanced gold nanostars coated with a thin silica shell, which tightly follow the nanostar morphology, are synthesized. An optimal spectral overlap between the multiple plasmon resonances of the nanostars and the luminescence of the emitting polymers is one key for the substantial increase of the electroluminescence. The second key ingredient is the star-shaped morphology. Experiments quantifying the photoluminescence, electroluminescence, and the current–voltage characteristics reveal that the physical origins of the improved performance are twofold; first, a plasmon mediated increase of the radiative recombination of excitons, and second, an improved outcoupling of light otherwise trapped inside the OLEDs. The thin silica shell apparently minimizes exciton quenching via energy transfer and prevents the nanostars from short-cutting the active layer.

Laser-induced plasma spectroscopy (LIPS) with a frequency-quadrupled Nd:YAG laser (266 nm, pulse duration: 4 ns) was applied to a metallic layer system consisting of an electrodeposited copper layer (30 μm) on an aluminium substrate. A stratigraphic model describing the emission signal in dependence of the pulse number was developed, which can explain several effects originating from laser ablation of various thin top layers by means of the Gaussian beam cross section character. This model was applied to trace elements through layers with thicknesses that are in the range of the resolvable depth, given by the single-pulse ablation rate, by means of empirical fitting functions. Additionally, the contribution of redeposited bulk material to the characteristic shape of emission-traces when averaging spot arrays with varying spacing could be quantified. This can be used to estimate cross-contamination in analytical applications where ablations need to be performed at close spacing.

Here, we report that hybrid multilayered plasmonic nanostars can be universally used as feedback agents for coherent random lasing in polar or nonpolar solutions containing gain material. We show that silver-enhancement of gold nanostars reduces the pumping threshold for coherent random lasing substantially for both a typical dye (R6G) and a typical fluorescent polymer (MEH-PPV). Further, we reveal that the lasing intensity and pumping threshold of random lasers based on silver-enhanced gold nanostars are not influenced by the silica coating, in contrast to gold nanostar-based random lasers, where silica-coated gold nanostars support only amplified spontaneous emission but no coherent random lasing.

A non-destructive, in-line, and low-cost focusing device based on an image sensor has been developed and demonstrated. It allows an in situ focus determination for a broad variety of laser types (e.g. cw and pulsed lasers). It provides stringent focusing conditions with high numerical apertures. This approach does not require sub-picosecond and/or auxiliary lasers, or high fluences above damage thresholds. Applications of this system include, but are not limited to the laser-illumination of micro-electrodes, pump-probe microscopy on thin films, and laser ablation of small samples without sufficient surface area for focus determination by ablation. An uncertainty of the focus position by an order of magnitude less than the respective Rayleigh length could be demonstrated.

The potential of fruit storage facilities that are contaminated with the widely used chemical antioxidant diphenylamine to cross-contaminate untreated apples (Malus × domestica Borkh.) was studied. A new sample preparation method identified the storage room paint, contaminated from past treatments, as the major source of cross-contamination in the analyzed facilities. Diphenylamine amounts of up to 917 g were found in a single storage room and were shown to correlate with the extent of cross-contamination on stored apples. Our data support a diffusion-based mechanism where the wall paint releases the antioxidant to the storage room atmosphere even years after the last treatment. Given the extent of cross-contamination found in our model experiments and under commercial storage conditions, we deduce a significant risk of exceeding the potentially upcoming maximum residue level of 0.01 mg kg(-1) on stored fruit in contaminated rooms even years after the last diphenylamine treatment.

Here we report on promising strategies for photon management in organic optolectronic devices. Multilayered hybrid plasmonic nanostars are used to boost the performance of organic light-emitting diodes (OLEDs). We designed and synthesized silver-enhanced gold nanostars coated with a very thin silica layer (∼10 nm), so that the hot-spots at the tips of the nanostars remain easily accessible, while the emission quenching is reduced. The spectral position of the plasmon resonances is tuned in specific spectral regions for the optimal overlap with the emission of different organic semiconductors and dyes. We successfully incorporated the nanostars in the active layer of fully working OLEDs. For a given current density, the plasmonic OLEDs show both: significantly enhanced electroluminescence as well as substantially different emission directionality as compared to the conventional plain OLEDs. We find that the nanostars act as nanoantennas, thus accelerating the radiative recombination of excitons as well as improving the out-coupling of light otherwise trapped in the OLEDs [1]. Furthermore, we demonstrate that hybrid multilayered plasmonic nanostars can be universally used as feedback agents for coherent random lasing in polar or non-polar solutions containing gain material [2, 3]. We show that the pumping threshold for coherent random lasing is reduced substantially upon silver-enhancement of gold nanostars. In addition, we reveal that neither pumping threshold nor the lasing intensity of random lasers based on silver-enhanced gold nanostars is influenced by silica coating, in contrast to gold nanostar-based random lasers, where silica coated gold nanostars support only amplified spontaneous emission but no coherent random lasing.