Holographic display with tilted spatial light modulator

Author(s): Tomasz Kozacki Abstract: “In this paper, we analyze a holographic display system utilizing a phase-only spatial light modulator (SLM) based on liquid crystal on silicon (LCoS). An LCoS SLM works in reflection, and, in some applications, it is convenient to use with an inclined illumination. Even with a highly inclined illumination, the holographic display is capable of good-quality image generation. We show that the key to obtain high-quality reconstructions is the tilt-dependent calibration and algorithms. Typically, an LCoS SLM is illuminated with a plane wave with normal wave vector. We use inclined illumination, which requires development of new algorithms…

A high speed wavefront determination method based on spatial frequency modulations for focusing light through random scattering media

Author(s): Meng Cui Abstract: “A large number of degrees of freedom are required to produce a high quality focus through random scattering media. Previous demonstrations based on spatial phase modulations suffer from either a slow speed or a small number of degrees of freedom. In this work, a high speed wavefront determination technique based on spatial frequency domain wavefront modulations is proposed and experimentally demonstrated, which is capable of providing both a high operation speed and a large number of degrees of freedom. The technique was employed to focus light through a strongly scattering medium and the entire wavefront was…

Dynamic generation of Debye diffraction-limited multifocal arrays for direct laser printing nanofabrication

Author(s): Han Lin, Baohua Jia, and Min Gu Abstract: “We propose a Debye-theory-based iterative method to produce accurate phase patterns for generating highly uniform diffraction-limited multifocal arrays with a high-NA objective. It is shown that by using the Debye method, the uniformity of the diffraction-limited focal arrays can reach 99%, owing to the critical consideration of the depolarization effect associated with high-NA objectives. The generated phase patterns are implemented in fast dynamic laser printing nanofabrication for the generation of individually controlled high-quality microvoid arrays in a solid polymer material by a single exposure of a femtosecond laser beam. As a…

Frequency bandwidth of light focused through turbid media

Author(s): Frerik van Beijnum, Elbert G. van Putten, Ad Lagendijk, and Allard P. Mosk Abstract: “We study the effect of frequency detuning on light focused through turbid media. By shaping the wavefront of the incident beam light is focused through an opaque scattering layer. When detuning the laser we observe a gradual decrease of the focus intensity, while the position, size,and shape of the focus remain the same within experimental accuracy. The frequency dependence of the focus intensity follows a measured speckle correlation function. We support our experimental findings with calculations based on transport theory. Our results imply wavefront shaping…

A SAR multilook optronic processor for operational Earth monitoring applications

Author(s): Linda Marchese, Pascal Bourqui, Sandra Turgeon, Michel Doucet, Carl Vachon, François Châteauneuf, Alain Bergeron, Bernd Harnisch and Martin Suess. Abstract: “Synthetic Aperture Radar (SAR) is the only remote sensing technology that can provide high resolution images in adverse weather conditions and in day or night times. It is thus is a powerful tool for Earth monitoring. Certain applications, such as disaster relief, military reconnaissance and ice-flow and ship monitoring require a continuous flow of high-resolution images covering large areas; however, given the large amount of complex data generated and system limitations of data bandwidth and processing speed, not all…

Imaging through turbid layers by scanning the phase conjugated second harmonic radiation from a nanoparticle

Author(s): Chia-Lung Hsieh, Ye Pu, Rachel Grange, Grégoire Laporte, Demetri Psaltis Abstract: “We demonstrate imaging through a turbid layer by using digital phase conjugation of the second harmonic field radiated from a beacon nanoparticle. We show that the phase-conjugated focus can be displaced from its initial position by illuminating the same region of the turbid layer with an angular offset. An image is obtained by scanning the phase-conjugated focus through the turbid layer in a region around the nanoparticle. We obtain a clear image of the target by measuring the light transmitted through it when scanning the focused beam.” Link…

Reconfigurable all-diffractive optical filters using phase-only spatial light modulators

Author(s): Gladys Mínguez-Vega, V. R. Supradeepa, Omel Mendoza-Yero, Andrew M. Weiner Abstract: “We demonstrate a reconfigurable optical filter implemented using a phase-only two-dimensional liquid-crystal-on-silicon spatial light modulator. To achieve this we utilize two different approaches leading to two different configurations in the modulator. The first one, based on a spatially patterned diffractive lens, permits us to obtain the desired spectrum along the optical axis and, in the second one, which is based on a generalized spectrometer, the desired spectrum is found outside of the optical axis. Experimental results show good agreement with the theory and indicate the validity of this…

Nonlinear response studies and corrections for a liquid crystal spatial light modulator

Author(s): RAVINDER KUMAR BANYAL, B. RAGHAVENDRA PRASAD Abstract: “The nonlinear response of light transmission characteristics of a liquid crystal (LC) spatial light modulator (SLM) is studied. The results show that the device exhibits a wide range of variations with different control parameters and input settings. Experiments were performed to obtain intensity modulation that is best described by either power-law or sigmoidal functions. Based on the inverse transformation, an appropriate pre-processing scheme for electrically addressed input gray-scale images, particularly important in several optical processing and imaging applications, is suggested. Further, the necessity to compensate the SLM image nonlinearities in a volume…

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…

PHASE MEASUREMENT OF OPTICAL WAVEFRONT BY AN SLM DIFFERENTIATION FILTER

Author(s): Hideo Furuhashi, Javier Valle Mayorga, Yoshiyuki Uchida, Akihiro Kono Abstract: “A system is proposed that employs a spatial light modulator as a differentiation filter to measure the phase of an optical wavefront. The pattern, position and orientation of the filter can be controlled electrically. This system measures the phase derivative of a wavefront that passes through a transparent phase object. The 3D shape of the object can be calculated by integrating the phase derivative.” Link to Publications Page Publication: XIX IMEKO World Congress, (free download) Issue/Year/DOI: XIX IMEKO World Congress, Fundamental and Applied Metrology, September 6−11, 2009

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