Advanced Scanning Laser-Doppler Vibrometer with Computer Generated Holograms

Author(s): S. Zwick, M. Warber, T. Haist, F. Schaal, W. Osten, S. Boedecker, and C. Rembe

Abstract:

“In this paper we present a novel technique for steering the beam of a scanning laser-Doppler vibrometer (LDV) using a Spatial Light Modulator (SLM). Computer Generated Holograms (CGH) are employed to obtain the phase maps displayed by the SLM. Due to this approach, spurious diffraction orders are generated. We present concepts to suppress these diffraction orders so as to realize a scanning vibrometer. We discuss the properties and limitations of this solution. Different SLMs have been evalutated and a compact scanning vibrometer based on a Holoeye Pluto SLM has been realized. First measurement results are presented. In addition, we demonstrate simulations on the reduction of speckle related signal dropouts. Drop-Outs can be reduced by adapting the measurement-beam wavefront with the CGH to maximize the light power collected with the vibrometer aperture. We have explored an approach to optimize the signal strength by adapting the coefficients of the Zernike polynomials of an additional wavefront shift.”

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Publication: AIP Conference Proceedings
Issue/Year: AIP Conf. Proc., Volume 1253, pp. 279-290, May 28, 2010
DOI: 10.1063/1.3455467

Digital phase conjugation of second harmonic radiation emitted by nanoparticles in turbid media

Author(s): Chia-Lung Hsieh, Ye Pu, Rachel Grange, and Demetri Psaltis

Abstract:

“We demonstrate focusing coherent light on a nanoparticle through turbid media based on digital optical phase conjugation of second harmonic generation (SHG) field from the nanoparticle. A SHG active nanoparticle inside a turbid medium was excited at the fundamental frequency and emitted SHG field as a point source. The SHG emission was scattered by the turbid medium, and the scattered field was recorded by off-axis digital holography. A phase-conjugated beam was then generated by using a phase-only spatial light modulator and sent back through the turbid medium, which formed a nearly ideal focus on the nanoparticle.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 18, Issue 12, pp. 12283-12290 (2010)
DOI: 10.1364/OE.18.012283

Direct creation of a photoinduced metallic structure and its optical properties in the terahertz frequency region

Author(s): Takanori Okada, Kazufumi Ooi, Yosuke Nakata, Koji Fujita, Katsuhisa Tanaka, Koichiro Tanaka

Abstract:

“We investigate the surface electromagnetic characteristics of a photoinduced periodical structure using the attenuated total reflection (ATR) technique in the terahertz frequency region. A wire grating structure is generated at the surface of a silicon prism by irradiation with a spatially modulated, ultrafast pulsed laser. A characteristic minimum due to the excitation of surface waves is observed in the ATR spectrum. The depth profile of the photoinduced carrier layer is also studied. We confirm that the photoinduced structure has metallic properties. This fabrication technique will be developed as a simple method to create “active” structures.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 35, Issue 10, pp. 1719-1721 (2010)
DOI: 10.1364/OL.35.001719

Materials for an Updatable Holographic 3D Display

Author(s): Cory W. Christenson, Pierre-Alexandre Blanche, Savas Tay, Ram Voorakaranam, Tao Gu, Weiping Lin, Peng Wang, Michiharu Yamamoto, Jayan Thomas, Robert A. Norwood, and Nasser Peyghambarian

Abstract:

“Holography is a powerful technique for providing high-resolution, realistic three-dimensional (3D) images without the need for special eyewear. A material that takes full advantage of the potential of holography, including updatability, has not existed. Here, the first updatable holographic 3D display based on a photorefractive polymer is summarized. The performance characteristics of these materials are measured, and how they relate to the development of additional display enhancements such as pulsed writing, white light viewing, and large viewing angle, are discussed.”

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Publication: Journal of Display Technology
Issue/Year: Journal of Display Technology, Issue: 99, pp1-7, (2010)
DOI: 10.1109/JDT.2010.2046620

Image Transmission Through an Opaque Material

Author(s): S. M. Popoff, G. Lerosey, M. Fink, A.C. Boccara, S. Gigan

Abstract:

“Optical imaging relies on the ability to illuminate an object and to collect and make sense of the light it scatters or transmit. Propagation through complex media such as biological tissues was so far believed to degrade the attainable depth as well as the resolution for imaging cite{sebbah2001introduction} because of multiple scattering. This is why such media are usually considered opaque. Recent experiments have demonstrated that multiply scattered light can in fact be harnessed thanks to wavefront control, and even put to profit to surpass what one can achieve within a homogenous medium in terms of focusing. Very recently, we have proven that it is possible to measure the complex mesoscopic optical transmission channels that allow light to traverse through an opaque medium. Here we show that we can optimally exploit those channels to coherently transmit and recover with a high fidelity an arbitrary image, independently of the complexity of the propagation. Our approach gives a general framework for coherent imaging in complex media, going well beyond focusing. It is valid for any linear complex media, and could be extended to several novel photonic materials, whatever the amount of scattering or disorder (from complete disorder to weakly disordered photonic crystals, and from superdiffusive to Anderson localization). ”

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Publication:arXiv.org / physics
Issue/Year:arXiv:1005.0532 (May 2010)