H. P. Urbach

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We experimentally demonstrate that a femtosecond frequency comb laser can be applied as a tool for long-distance measurement in air. Our method is based on the measurement of cross correlation between individual pulses in a Michelson interferometer. From the position of the correlation functions, distances of up to 50 m have been measured. We have compared(More)
We experimentally demonstrate long distance measurements with a femtosecond frequency comb laser using dispersive interferometry. The distance is derived from the unwrapped spectral phase of the dispersed interferometer output and the repetition frequency of the laser. For an interferometer length of 50 m this approach has been compared to an independent(More)
  • Op J T Gezag Van De Rector Magnificus, Fokkema, +10 authors A Gisolf
  • 2005
Dr. F. Bociort has provided substantial guidance and support in the preparation of this thesis. 1.1. Historical overview of imaging systems development Image formation is the main application of traditional optical systems such as loupe, telescope, microscope, camera, etc. In fact, lenses form images even if this is not their intended purpose. The history(More)
We present a broadband quantum cascade laser-based spectroscopic system covering the region between 850 and 1250 cm(-1). Its robust multipass cavity ensures a constant interaction length over the entire spectral region. The device enables the detection and identification of numerous molecules present in a complex gas mixture without any pre-treatment in two(More)
We apply a phase retrieval algorithm to the intensity pattern of a Hartmann wavefront sensor to measure with enhanced accuracy the phase structure of a Hartmann hole array. It is shown that the rms wavefront error achieved by phase reconstruction is one order of magnitude smaller than the one obtained from a typical centroid algorithm. Experimental results(More)
Recently, efforts have been made to improve ptychography phase retrieval algorithms so that they are more robust against noise. Often the algorithm is adapted by changing the cost functional that needs to be minimized. In particular, it has been suggested that the cost functional should be obtained using a maximum-likelihood approach that takes the noise(More)
We present a concealing method in which an anti-point spread function (APSF) is generated using binary optics, which produces a large-scale dark area in the focal region that can hide any object located within it. This result is achieved by generating two identical PSFs of opposite signs, one consisting of positive electromagnetic waves from the zero-phase(More)
Typically, metal particles are difficult to manipulate with conventional optical vortex (OV) tweezers, because of their strong absorption and scattering. However, it has been shown that the vortex field of surface plasmonic polaritons, called plasmonic vortex (PV), is capable of stable trapping and dynamic rotation of metal particles, especially those of(More)
Monitoring the cells' apoptosis progression could provide a valuable insight into the temporal events that initiate cell death as well as the potential for rescue of apoptotic cells. In this paper, we engineered a novel and robust method for monitoring apoptosis of tumor cells based on dynamic laser tweezers, using A549 and HeLa cell line as typical(More)