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Author

Mischa Megens

Other affiliations: Princeton University
Bio: Mischa Megens is an academic researcher from Philips. The author has contributed to research in topics: Magnetic nanoparticles & Optical fiber. The author has an hindex of 14, co-authored 28 publications receiving 1764 citations. Previous affiliations of Mischa Megens include Princeton University.

Papers
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Journal ArticleDOI
TL;DR: In this article, a photonic-crystal structure for superior optical mode control was proposed for blue light-emitting diodes with a light extraction efficiency of 73% using InGaN-GaN devices.
Abstract: Blue light-emitting diodes with a light extraction efficiency of 73% are reported. The InGaN–GaN devices use a photonic-crystal structure for superior optical mode control; their performance has been characterized experimentally and modelled theoretically.

716 citations

Journal ArticleDOI
18 Aug 2005-Nature
TL;DR: Three-dimensional icosahedral quasicrystals exhibit sizeable stop gaps and, despite their quasiperiodicity, yield uncomplicated spectra that allow us to experimentally determine the faces of their effective Brillouin zones, confirming that they are excellent candidates for photonic bandgap materials.
Abstract: Quasicrystalline structures may have optical bandgap properties — frequency ranges in which the propagation of light is forbidden — that will make them well suited for applications in which photonic crystals are normally used. Previous work has focused on one- and two-dimensional quasicrystals for which exact theoretical calculations can be made. But when it comes to three dimensions, computation of the optical properties remains a tough challenge. Man et al. tackled the three-dimensional case experimentally using a large photonic quasicrystal made of plastic. They find that the periodic structure yields surprisingly simple spectra, and the resulting structural insights confirm that quasicrystals are excellent candidates for photonic bandgap materials. Quasicrystalline structures may have optical bandgap properties—frequency ranges in which the propagation of light is forbidden—that make them well-suited to the scientific and technological applications for which photonic crystals1,2,3 are normally considered4. Such quasicrystals can be constructed from two or more types of dielectric material arranged in a quasiperiodic pattern whose rotational symmetry is forbidden for periodic crystals (such as five-fold symmetry in the plane and icosahedral symmetry in three dimensions). Because quasicrystals have higher point group symmetry than ordinary crystals, their gap centre frequencies are closer and the gaps widths are more uniform—optimal conditions for forming a complete bandgap that is more closely spherically symmetric. Although previous studies have focused on one-dimensional and two-dimensional quasicrystals4,5,6,7, where exact (one-dimensional) or approximate (two-dimensional) band structures can be calculated numerically, analogous calculations for the three-dimensional case are computationally challenging and have not yet been performed. Here we circumvent the computational problem by doing an experiment. Using stereolithography, we construct a photonic quasicrystal with centimetre-scale cells and perform microwave transmission measurements. We show that three-dimensional icosahedral quasicrystals exhibit sizeable stop gaps and, despite their quasiperiodicity, yield uncomplicated spectra that allow us to experimentally determine the faces of their effective Brillouin zones. Our studies confirm that they are excellent candidates for photonic bandgap materials.

233 citations

Journal ArticleDOI
TL;DR: In this article, face-centered cubic-like lattices with periods of 0.9 μm were created by interference of multiple visible laser beams on photosensitive epoxy, and defect-free porous structures were obtained in an area covered by the laser beams.
Abstract: Face-centered cubiclike lattices with periods of 0.9 μm were created by interference of multiple visible laser beams on photosensitive epoxy. Defect-free porous structures were obtained in an area ...

204 citations

Journal ArticleDOI
TL;DR: In this article, the authors present an overview of miniaturized biosensor devices based on the sensitive detection of magnetic nanoparticles using the giant magneto-resistance effect, which has advantages over established methods, and the sensitivity is promising.

151 citations

Journal ArticleDOI
TL;DR: In this article, the shape of the emission profile, the intrinsic spectrum of emitting dipoles and the emitting dipole orientation were measured using a microcavity light outcoupling model.
Abstract: Determining the precise shape of the emission profile across the thickness of the active layer in organic light-emitting diodes is of importance for device optimization and assessing the validity of advanced device models. We present a comprehensive method for accurately measuring the shape of the emission profile, the intrinsic spectrum of emitting dipoles and the emitting dipole orientation. The method uses a microcavity light outcoupling model, which includes self-absorption and optical anisotropy, and is based on the full wavelength, angle and polarization resolved emission intensity. Application to blue (polyfluorene-based) and orange-red (NRS-PPV) polymer organic light-emitting diodes reveals a peaked shape of the emission profile. A significant voltage and layer thickness dependence of the peak positions is observed, with a demonstrated resolution better than 5 nm.

87 citations


Cited by
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Proceedings Article
01 Jan 1999
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

2,722 citations

PatentDOI
06 Apr 2012-Science
TL;DR: In this article, the authors present stretchable and printable semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed, or otherwise deformed.
Abstract: The present invention provides stretchable, and optionally printable, semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed. Stretchable semiconductors and electronic circuits of the present invention preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention may be adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.

1,673 citations

Journal ArticleDOI
07 Mar 2008-Sensors
TL;DR: In this article, the most common traditional traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, including nanowire or magnetic nanoparticle-based biosensing.
Abstract: Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response.

1,550 citations

PatentDOI
TL;DR: In this article, the authors present methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations.
Abstract: The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of ‘soft adhesion’ to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

1,305 citations

Journal ArticleDOI
TL;DR: The potentials and limitations of analysis with lateral flow (immuno)assays are illustrated using a literature survey and a SWOT analysis (acronym for “strengths, weaknesses, opportunities, threats”).
Abstract: Lateral flow (immuno)assays are currently used for qualitative, semiquantitative and to some extent quantitative monitoring in resource-poor or non-laboratory environments. Applications include tests on pathogens, drugs, hormones and metabolites in biomedical, phytosanitary, veterinary, feed/food and environmental settings. We describe principles of current formats, applications, limitations and perspectives for quantitative monitoring. We illustrate the potentials and limitations of analysis with lateral flow (immuno)assays using a literature survey and a SWOT analysis (acronym for “strengths, weaknesses, opportunities, threats”). Articles referred to in this survey were searched for on MEDLINE, Scopus and in references of reviewed papers. Search terms included “immunochromatography”, “sol particle immunoassay”, “lateral flow immunoassay” and “dipstick assay”.

1,296 citations