Search results for "Beam expander"
showing 4 items of 4 documents
An Optical Remote Sensor for Fingerprint Identification using Speckle Pattern
2017
The implementation of a simple, inexpensive optical device for remote fingerprint identification is presented. The sensor is based on temporal tracking of back-reflected secondary speckle patterns generated while illuminating a finger with a laser.
Visible light apparatus for preliminary tests of x-ray optics
2006
We report a useful visible light testing procedure for a first analysis of soft X-ray grazing incidence optics (0.1-2 keV). Although diffraction is a limit in the application of this method, great advantages are obtained by running the tests in air with direct access to modify the geometrical mounting of the individual mirror shells. We present the experimental apparatus and show the first results of the investigation of light weight optics based on plastic foil material and comparison with results obtained with an X-ray beam.
Isotropic compensation of diffraction-driven angular dispersion
2007
We report on an optical arrangement capable of compensating angular dispersion of paraxial wave fields developed by diffractive optical elements (DOEs). Schematically, the system is a beam expander in which two phase-only zone plates have been inserted, remaining afocal the coupled system. The DOE, which induces a continuous set of dispersive tilted plane waves, is placed at a specific position within the proposed setup providing an output spectrum with achromatic angular deviation. A directional matching between phase fronts and pulse fronts of output wave packets is demonstrated.
Controlling the carrier-envelope phase of few-cycle focused laser beams with a dispersive beam expander
2008
We report on a procedure to focalize few-cycle laser pulses in dispersive media with controlled waveform. Stationarity of the carrier-envelope phase for extended depth of focus is attained by shaping the spatial dispersion of the ultrashort beam. An adjustable group velocity is locally tuned in order to match a prescribed phase velocity at focus. A hybrid diffractive-refractive lens system is proposed to drive the wavefield to an immersion microscope objective under convenient broadband modulation. Numerical simulations demonstrate robustness over positioning of this dispersive beam expander.