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Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the(More)
There is a strong need for low-cost biosensors to enable rapid, on-site analysis of biological, biomedical, or chemical substances. We propose a platform for label-free optical biosensors based on applying the analyte onto a surface-functionalized photonic crystal slab and performing a transmission measurement with two crossed polarization filters. This(More)
We present highly efficient electroluminescent devices using size-separated silicon nanocrystals (ncSi) as light emitting material. The emission color can be tuned from the deep red down to the yellow-orange spectral region by using very monodisperse size-separated nanoparticles. High external quantum efficiencies up to 1.1% as well as low turn-on voltages(More)
We use projection screens filled with colloidal dispersions to reduce laser speckle in laser projection systems. Laser light is multiply scattered at the globules of the colloidal dispersion's internal phase, which do Brownian movement. The integration time of the human eye causes a perception of a reduced laser speckle contrast because of temporal(More)
The photo-Dember effect is a source of impulsive THz emission following femtosecond pulsed optical excitation. This emission results from the ultrafast spatial separation of electron-hole pairs in strong carrier gradients due to their different diffusion coefficients. The associated time dependent polarization is oriented perpendicular to the excited(More)
We present a method to determine the speckle properties of front projection screens. Seven different screens are investigated in a backscattering geometry for 808 nm light. The speckle contrast reduction that results from polarization scrambling and reduced temporal coherence is modeled for the case of volume scattering in the screens. For this purpose, the(More)
We demonstrate low-speckle laser projection using a broad-area vertical-cavity surface-emitting laser (VCSEL) emitting at 840 nm wavelength as the illumination source. By driving the source in a nonmodal emission regime, we were able to achieve speckle contrast values as low as 3.5% in a realistic projection setup. This was done by driving the VCSEL with(More)
The efficiency of organic bulk heterojunction solar cells strongly depends on the multiscale morphology of the interpenetrating polymer-fullerene network. Understanding the molecular assembly and the identification of influencing parameters is essential for a systematic optimization of such devices. Here, we investigate the molecular ordering during the(More)
As an application of organic semiconductor distributed feedback (DFB) lasers we demonstrate their use as excitation sources in Raman spectroscopy. We employed an efficient small molecule blend, a high quality resonator and a novel encapsulation method resulting in an improved laser output power, a reduced laser line width and an enhanced power stability.(More)
Size-selective precipitation was used to successfully separate colloidally stable allylbenzene-capped silicon nanocrystals into several visible emitting monodisperse fractions traversing the quantum size effect range of 1-5 nm. This enabled the measurement of the absolute quantum yield and lifetime of photoluminescence of allylbenzene-capped silicon(More)