Holographic optical tweezers with real-time hologram calculation using a phase-only modulating LCOS-based SLM at 1064 nm

Author(s): Andreas Hermerschmidt, Sven Krüger, Tobias Haist, Susanne Zwick, Michael Warber, Wolfgang Osten

Abstract:

“We present a method that enables the generation of arbitrary positioned dual-beam traps without additional hardware in a single-beam holographic optical tweezers setup. By this approach stable trapping at low numerical aperture and long working distance is realized with an inverse standard research microscope. Simulations and first experimental results are presented. Additionally we present first steps towards using the method to realize a holographic 4pi-microscope. We will also give a detailed analysis of the phase-modulating properties and especially the spatial-frequency dependent diffraction efficiency of holograms reconstructed with the phase-only LCOS spatial light modulator used in our system. Finally, accelerated hologram optimization based on the iterative Fourier transform algorithm is done using the graphics processing unit of a consumer graphics board.”

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Publication: SPIE Digital Library
Issue/Year: SPIE Proceedings, Vol. 6905, 690508 (2008),
DOI: 10.1117/12.764649

Stimulated emission depletion microscopy with a supercontinuum source and fluorescence lifetime imaging

Author(s): Egidijus Auksorius, Bosanta R. Boruah, Christopher Dunsby, Peter M. P. Lanigan, Gordon Kennedy, Mark A. A. Neil, and Paul M. W. French

Abstract:

“We demonstrate stimulated emission depletion (STED) microscopy implemented in a laser scanning confocal microscope using excitation light derived from supercontinuum generation in a microstructured optical fiber. Images with resolution improvement beyond the far-field diffraction limit in both the lateral and axial directions were acquired by scanning overlapped excitation and depletion beams in two dimensions using the flying spot scanner of a commercially available laser scanning confocal microscope. The spatial properties of the depletion beam were controlled holographically using a programmable spatial light modulator, which can rapidly change between different STED imaging modes and also compensate for aberrations in the optical path. STED fluorescence lifetime imaging microscopy is demonstrated through the use of time-correlated single photon counting.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 33, Issue 2, pp. 113-115, 2008
DOI: 10.1364/OL.33.000113

Demixing light paths inside disordered metamaterials

Author(s): I. M. Vellekoop, E. G. van Putten, A. Lagendijk, and A. P. Mosk

Abstract:

“We experimentally demonstrate the first method to focus light inside disordered photonic metamaterials. In such materials, scattering prevents light from forming a geometric focus. Instead of geometric optics, we used multi-path interference to make the scattering process itself concentrate light on a fluorescent nanoscale probe at the target position. Our method uses the fact that the disorder in a solid material is fixed in time. Therefore, even disordered light scattering is deterministic. Measurements of the probes fluorescence provided the information needed to construct a specific linear combination of hundreds of incident waves, which interfere constructively at the probe.”

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Publication:Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 1, pp. 67-80, 2008
DOI: 10.1364/OE.16.000067

Extended fractional wavelet joint transform correlator

Author(s): Alpana Bhagatji, Naveen K. Nishchal, Arun K. Gupta and B.P. Tyagi

Abstract:

“An extended fractional wavelet joint transform correlator is implemented for real-time target recognition applications. The real-time input scene captured using a charge-coupled device camera along with the reference image is fractional Fourier transformed. The obtained joint power spectrum is multiplied by an appropriately scaled wavelet filter and the resultant function is differentiated. The application of wavelet filter enhances the correlation outputs and differential processing of wavelet-filtered joint power spectrum improves the detection efficiency by reducing the zero-order spectra. Targets with Gaussian and speckle noise have also been used to check the correlation output. The performance metrics: correlation peak intensity, peak-to-correlation energy, peak-to-sidelobe ratio and signal to clutter ratio have been calculated. The experimental results are presented in support of the proposed idea.”

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Publication: Optics Communications
Issue/Year: Optics Communications Volume 281, Issue 1, 1 January 2008, Pages 44-48
DOI: 10.1016/j.optcom.2007.09.005