TY - JOUR A1 - Brixner, Tobias A1 - Pawłowska, Monika A1 - Goetz, Sebastian A1 - Dreher, Christian A1 - Wurdack, Matthias A1 - Krauss, Enno A1 - Razinskas, Gary A1 - Geisler, Peter A1 - Hecht, Bert T1 - Shaping and spatiotemporal characterization of sub-10-fs pulses focused by a high-NA objective N2 - We describe a setup consisting of a 4 f pulse shaper and a microscope with a high-NA objective lens and discuss the spects most relevant for an undistorted spatiotemporal profile of the focused beam. We demonstrate shaper-assisted pulse compression in focus to a sub-10-fs duration using phase-resolved interferometric spectral modulation (PRISM). We introduce a nanostructure-based method for sub-diffraction spatiotemporal characterization of strongly focused pulses. The distortions caused by optical aberrations and space–time coupling from the shaper can be reduced by careful setup design and alignment to about 10 nm in space and 1 fs in time. KW - Interference microscopy KW - Scanning microscopy KW - Subwavelength structures KW - nanostructures KW - Pulse shaping KW - Ultrafast measurements Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-111120 ER - TY - JOUR A1 - Rewitz, Christian A1 - Keitzl, Thomas A1 - Tuchscherer, Philip A1 - Goetz, Sebastian A1 - Geisler, Peter A1 - Razinskas, Gary A1 - Hecht, Bert A1 - Brixner, Tobias T1 - Spectral-interference microscopy for characterization of functional plasmonic elements JF - Optics Express N2 - Plasmonic modes supported by noble-metal nanostructures offer strong subwavelength electric-field confinement and promise the realization of nanometer-scale integrated optical circuits with well-defined functionality. In order to measure the spectral and spatial response functions of such plasmonic elements, we combine a confocal microscope setup with spectral interferometry detection. The setup, data acquisition, and data evaluation are discussed in detail by means of exemplary experiments involving propagating plasmons transmitted through silver nanowires. By considering and experimentally calibrating any setup-inherent signal delay with an accuracy of 1 fs, we are able to extract correct timing information of propagating plasmons. The method can be applied, e.g., to determine the dispersion and group velocity of propagating plasmons in nanostructures, and can be extended towards the investigation of nonlinear phenomena. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-85922 UR - http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-20-13-14632&id=238393 ER - TY - JOUR A1 - Gary, Sebastian A1 - Lenhard, Wolfgang A1 - Lenhard, Alexandra T1 - Modelling norm scores with the cNORM package in R JF - Psych N2 - In this article, we explain and demonstrate how to model norm scores with the cNORM package in R. This package is designed specifically to determine norm scores when the latent ability to be measured covaries with age or other explanatory variables such as grade level. The mathematical method used in this package draws on polynomial regression to model a three-dimensional hyperplane that smoothly and continuously captures the relation between raw scores, norm scores and the explanatory variable. By doing so, it overcomes the typical problems of classical norming methods, such as overly large age intervals, missing norm scores, large amounts of sampling error in the subsamples or huge requirements with regard to the sample size. After a brief introduction to the mathematics of the model, we describe the individual methods of the package. We close the article with a practical example using data from a real reading comprehension test. KW - regression-based norming KW - continuous norming KW - inferential norming KW - data smoothing KW - curve fitting KW - percentile estimation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284143 SN - 2624-8611 VL - 3 IS - 3 SP - 501 EP - 521 ER - TY - JOUR A1 - Lenhard, Alexandra A1 - Lenhard, Wolfgang A1 - Gary, Sebastian T1 - Continuous norming of psychometric tests: A simulation study of parametric and semi-parametric approaches JF - PLoS ONE N2 - Continuous norming methods have seldom been subjected to scientific review. In this simulation study, we compared parametric with semi-parametric continuous norming methods in psychometric tests by constructing a fictitious population model within which a latent ability increases with age across seven age groups. We drew samples of different sizes (n = 50, 75, 100, 150, 250, 500 and 1,000 per age group) and simulated the results of an easy, medium, and difficult test scale based on Item Response Theory (IRT). We subjected the resulting data to different continuous norming methods and compared the data fit under the different test conditions with a representative cross-validation dataset of n = 10,000 per age group. The most significant differences were found in suboptimal (i.e., too easy or too difficult) test scales and in ability levels that were far from the population mean. We discuss the results with regard to the selection of the appropriate modeling techniques in psychometric test construction, the required sample sizes, and the requirement to report appropriate quantitative and qualitative test quality criteria for continuous norming methods in test manuals. KW - statistical models KW - simulation and modeling KW - psychometrics KW - age groups KW - skewness KW - normal distribution KW - polynomials KW - statistical distributions Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200480 VL - 14 IS - 9 ER -