arXiv subjects

E. G. van Putten

Publications and source records attributed to E. G. van Putten.

5 recordsLinked to original sources

arXiv2011

Non-Imaging Speckle Interferometry forHigh Speed Nanometer-Scale Position Detection

We experimentally demonstrate a non-imaging approach to displacement measurement for complex scattering materials. By spatially controlling the wave front of the light that incidents on the material we concentrate the scattered light in a focus on a designated position. This wave front acts as an unique optical fingerprint that enables precise position detection of the illuminated material by simply measuring the intensity in the focus. By combining two optical fingerprints we demonstrate position detection along one dimension with a displacement resolution of 2.1 nm. As our approach does not require an image of the scattered field, it is possible to employ fast non-imaging detectors to enable high-speed position detection of scattering materials.

physics.optics↗

arXiv2011

Scattering Lens Resolves sub-100 nm Structures with Visible Light

The smallest structures that conventional lenses are able to optically resolve are of the order of 200 nm. We introduce a new type of lens that exploits multiple scattering of light to generate a scanning nano-sized optical focus. With an experimental realization of this lens in gallium phosphide we have succeeded to image gold nanoparticles at 97 nm optical resolution. Our work is the first lens that provides a resolution in the nanometer regime at visible wavelengths.

physics.optics↗

arXiv2010

Optimal Concentration of Light in Turbid Materials

In turbid materials it is impossible to concentrate light into a focus with conventional optics. Recently it has been shown that the intensity on a dyed probe inside a turbid material can be enhanced by spatially shaping the wave front of light before it enters a turbid medium. Here we show that this enhancement is due to concentration of light energy to a spot much smaller than a wavelength. We focus light on a dyed probe sphere that is hidden under an opaque layer. The light is optimally concentrated to a focus which does not exceed the smallest focal area physically possible by more than 68%. A comparison between the intensity enhancements of both the emission and excitation light supports the conclusion of optimal light concentration.

physics.optics↗

arXiv2008

Spatial amplitude and phase modulation using commercial twisted nematic LCDs

We present a method for full spatial phase and amplitude control of a laser beam using a twisted nematic liquid crystal display combined with a spatial filter. By spatial filtering we combine four neighboring pixels into one superpixel. At each superpixel we are able to independently modulate the phase and the amplitude of light. We demonstrate experimentally the independent phase and amplitude modulation using this novel technique. Our technique does not impose special requirements on the spatial light modulator and allows precise control of fields even with imperfect modulators.

physics.optics↗

arXiv2006

Recognition of paper samples by correlation of their speckle patterns

Buchanan et al. [Nature 436, p. 475 (2005)] have shown that it is possible to recognize paper samples via their speckle pattern by using a line-shaped laser focus, four photo detectors and a scanning mechanism. In this report recognition of five out of ten paper samples is presented. The sample was illuminated by a 2.62 +- 0.02 mm circular spot and the reflected light was measured by a static CCD. We have formulated a criterion for recognition that limits the probability of false recognition to 0.1 % for the experiment with ten samples. We obtained results that show that the probability of false recognition will be negligible for a large amount of samples. The properties of speckle originating from a line and a spot illumination source have been compared to see whether the use of a line results in major advantages for the recognition of samples.

physics.ed-ph↗