Andreas Mischok

Andreas Mischok
University of Cologne | UOC · Humboldt-Centre for Nano- and Biophotonics

Dr.

About

43
Publications
4,885
Reads
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494
Citations
Additional affiliations
October 2011 - June 2016
Technische Universität Dresden
Position
  • PhD Student
Education
October 2007 - October 2012
Technische Universität Dresden
Field of study
  • Physics

Publications

Publications (43)
Article
Full-text available
Blending organic electron donors and acceptors yields intermolecular charge-transfer states with additional optical transitions below their optical gaps. In organic photovoltaic devices, such states play a crucial role and limit the operating voltage. Due to its extremely weak nature, direct intermolecular charge-transfer absorption often remains u...
Article
Full-text available
Strong light-matter coupling can re-arrange the exciton energies in organic semiconductors. Here, we exploit strong coupling by embedding a fullerene-free organic solar cell (OSC) photo-active layer into an optical microcavity, leading to the formation of polariton peaks and a red-shift of the optical gap. At the same time, the open-circuit voltage...
Article
Full-text available
Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with µm-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air and...
Article
Strong light–matter coupling leads to the formation of mixed exciton–polariton states, allowing for a rigorous manipulation of the absorption and emission of excitonic materials. Here, we demonstrate the realization of this promising concept in organic photodetectors. By hybridizing the E11 exciton of semiconducting (6,5) single-walled carbon nanot...
Article
Full-text available
Photonic band structure engineering has developed into an important technique for controlling the emission and interaction of photons and polaritons in microcavities. In this work, lasing from defect states in photonic Kronig‐Penney structures embedded into metal‐organic microcavities is demonstrated. As compared to the more delocalized lasing stat...
Preprint
Organic exciton-photon polariton lasers have recently been shown to be remarkable candidates for the realization of efficient sources of coherent light operating at room temperature. While their thresholds are now comparable with conventional organic photon lasers, tuning of molecular conformation and orientation as a means to further enhance their...
Preprint
The use of thermally activated delayed fluorescence emitters and emitters that show preferential horizontal orientation of their transition dipole are two emerging strategies to enhance the efficiency of organic light-emitting diodes. We present the first example of a liquid crystalline multi-resonance thermally activated delayed fluorescent emitte...
Article
Exciplexes of individual electron donor and acceptor molecules are a promising approach to utilizing otherwise non-emissive triplet states in optoelectronic applications. In this work, we synthesize a series of bis(terpyridine)...
Article
Full-text available
The combination of organics and metals in a composite film holds promise for combining plasmonic interaction with gain and for the realization of epsilon-near-zero (ENZ) metamaterials. In particular, fluorescent organic dyes can be used to compensate the plasmonic losses of a homogenized metal-organic material. Here, we fabricate such films through...
Conference Paper
Electrically pumped emission of light-matter exciton-polaritons is of great fundamental and practical interest but so far suffers from poor efficiency. Here, we present a universal strategy to generate polariton emission from state-of-the-art organic light emitting diodes (OLED). We demonstrate green and red emitting devices reaching an external qu...
Preprint
Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with $\mu$m-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air...
Article
Full-text available
Fluorescence imaging is an indispensable tool in biology, with applications ranging from single‐cell to whole‐animal studies and with live mapping of neuronal activity currently receiving particular attention. To enable fluorescence imaging at cellular scale in freely moving animals, miniaturized microscopes and lensless imagers are developed that...
Patent
A method for detecting infrared electromagnetic radiation and for converting same into an electrical signal, an optoelectronic component, in particular an organic infrared detector for (near) infrared detection, and use thereof for detecting an electromagnetic signal in the wavelength range of 780 nm to 10 μm, are provided.
Article
Organic microcavities provide unique properties that are highly advantageous for designing microlasers, but lack in efficient ways to directly integrate electrodes able to drive high currents. The introduction of thin, patterned metal films, leading to the formation of local Tamm plasmon polariton states, has been recently demonstrated as a possibl...
Conference Paper
Here, we demonstrate the successful application of organic light-emitting diodes in optogenetics to control neurons in fruit fly larvae and explore their further use as a light source in fluorescence microscopy.
Article
We present organic near-infrared photodetectors based on the absorption of charge-transfer (CT) states at the zinc-phthalocyanine - C60 interface. By using a resonant optical cavity device architecture, we achieve a narrowband detection, centered around 1060 nm and well below (>200nm) the optical gap of the neat materials. We measure transient phot...
Article
Full-text available
Organic spectrometers are attractive for biomedicine and industrial process monitoring but are currently limited in terms of spectral selectivity and the accessible wavelength range. Here, we achieve narrowband enhancement of the below-gap near-infrared response of charge-transfer (CT) excitations in organic photodiodes by introducing them into a h...
Article
We observe lasing emission from an organic microcavity structure at room temperature with a sunflower-like pattern closely resembling Laguerre-Gauss modes. Simultaneously, measured angle-resolved emission spectra below and above the lasing threshold demonstrate the coexistence of discrete modes, confined in a doughnut-shaped potential, and continuo...
Article
Spectroscopic photodetection is a powerful tool in disciplines such as medical diagnosis, industrial process monitoring, or agriculture. However, its application in novel fields, including wearable and biointegrated electronics, is hampered by the use of bulky dispersive optics. Here, solution-processed organic donor-acceptor blends are employed in...
Conference Paper
Organic materials offer fascinating properties for realizing optoelectronic devices such as organic light emitting diodes (OLEDs) and solar cells (OSCs). The performance of the latter is mainly determined by the low operating voltage with respect to the optical band gap and the limited absorption properties of organic materials in the near infrared...
Data
Blending organic electron donors and acceptors yields intermolecular charge-transfer states with additional optical transitions below their optical gaps. In organic photovoltaic devices, such states play a crucial role and limit the operating voltage. Due to its extremely weak nature, direct intermolecular charge-transfer absorption often remains u...
Data
Supplementary Figures, Supplementary Tables, Supplementary Notes, Supplementary Discussion, Supplementary Methods and Supplementary References
Conference Paper
Two of the most successful microresonator concepts are the vertical cavity surface emitting laser (VCSEL), comprising a vertical cavity of highly reflective DBRs sandwiching an active layer, and the distributed feedback (DFB) laser, where a periodic optical grating selects laser modes from an active waveguide (WG) layer. Here, an organic microcavit...
Article
Full-text available
A. Mischok and co-workers develop a hybrid waveguide–vertical cavity surface emitting laser on page 1215. An angle-resolved emission spectrum of such a hybrid laser is presented on their cover image. The linear dispersion lines of an organic waveguide are scattered into the surface emission of a microcavity via a high-order diffraction grating and...
Article
Full-text available
We report on cross-coupled composite-cavity microresonators consisting of a vertical cavity and a second-order distributed feedback structure which employ the same organic active medium and support surface-normal and in-plane emission at the same time. The optical coupling is due to a first-order light diffraction on a second-order Bragg grating an...
Article
Hybrid resonators in vertical and lateral direction are introduced by depositing a full vertical cavity surface emitting laser (VCSEL) stack on top of a periodically structured substrate. As a result, waveguided (WG) modes in the cavity plane are scattered into the vertical direction and exhibit linear dispersion curves in addition to the original...
Article
We report a room temperature study of net gain far below the lasing threshold in planar organic microresonators with a limited amount of gain material. We measure the net gain change as a function of optical pump power for various resonator designs and cavity thicknesses by carefully analyzingspatially filtered emission spectra of the microcavity u...
Article
Full-text available
Organic microcavities comprising the host:guest emitter system Alq3:DCM offer an interesting playground to experimentally study the dispersion characteristics of laterally patterned microlasers due to the broad emission spectrum and large oscillator strength of the organic dye. By structuring of metallic or dielectric sublayers directly on top of t...
Article
Abstract We embed periodic SiO2 wires in an organic microcavity, producing a rectangular potential by the different optical thicknesses of the active layer due to the additional SiO2 layer. By μ -photoluminescence spectroscopy, we observe the energy dispersion of the photons and obtain discrete localized below and extended Bloch states above the po...
Article
Full-text available
By adding photonic wire structures to an organic microcavity, we create an additional confinement and a Bloch-like band structure in the dispersion of periodically structured cavities. We experimentally observe spontaneous and stimulated emission from the ground and different excited discrete modes at room temperature. By changing the spatial gain...
Article
We investigate the angle-resolved emission of a multimode organic microcavity in a microscope, setup with a high numerical aperture. In the angle-integrated spectra, we observe the formation of narrow deep minima and maxima typical for Fano-like interference in microcavities. Our experimental angle-resolved transmission and emission spectra agree w...
Article
Full-text available
We investigate the formation of optical modes in organic microcavities with an incorporated perforated silver layer. The metal leads to a formation of Tamm-plasmon-polaritons and thus separates the sample into metal-free or metal-containing areas, supporting different resonances. This mode splitting is exploited to confine photons in elliptic holes...
Article
A one-dimensional periodic rectangular potential, also known as the Kronig-Penney (KP) potential, transforms the parabolic dispersion of a free particle into a set of bands separated by bandgaps. However, if the potential wells are deep enough, the lowest bands converge into a set of single discrete states, numbered from j = 1 to j = jmax, which ca...
Article
An organic microcavity is excited by blue and green pump lasers, showing bright coherent emission in the red. On page 746, A. Mischok et al. show how an additional plasmonic microstructure in the cavity leads to the formation of Tamm-Plasmon-Polariton states and an intricate far-field pattern, which enables the observation of photonic Bloch states....
Article
Full-text available
Due to their geometry, optical microcavities allow strong confinement of light between the mirrors and promise single mode operation at lowest possible lasing thresholds. Nevertheless, such devices suffer from losses not only due to parasitic absorption of the active or mirror layers, but especially via outcoupling of leaky and waveguided modes wit...
Article
Full-text available
We investigate the complex mode structure in microcavities with multidimensional optical confinement. Our active material is composed of the organic blend Alq3:DCM, embedded into a microcavity containing arrays of photonic wires, facilitating strong lateral confinement. We directly record the energy dispersion for one k⃗ vector component while the...

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