SLM Microscopy: Scanless Two-Photon Imaging and Photostimulation with Spatial Light Modulators

Author(s): Volodymyr Nikolenko, Brendon O. Watson, Roberto Araya, Alan Woodruff, Darcy S. Peterka and Rafael Yuste

Abstract:

“Laser microscopy has generally poor temporal resolution, caused by the serial scanning of each pixel. This is a significant problem for imaging or optically manipulating neural circuits, since neuronal activity is fast. To help surmount this limitation, we have developed a “scanless” microscope that does not contain mechanically moving parts. This microscope uses a diffractive spatial light modulator (SLM) to shape an incoming two-photon laser beam into any arbitrary light pattern. This allows the simultaneous imaging or photostimulation of different regions of a sample with three-dimensional precision. To demonstrate the usefulness of this microscope, we perform two-photon uncaging of glutamate to activate dendritic spines and cortical neurons in brain slices. We also use it to carry out fast (60 Hz) two-photon calcium imaging of action potentials in neuronal populations. Thus, SLM microscopy appears to be a powerful tool for imaging and optically manipulating neurons and neuronal circuits. Moreover, the use of SLMs expands the flexibility of laser microscopy, as it can substitute traditional simple fixed lenses with any calculated lens function.”

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Publication: Frontiers in Neural Circuits
Issue/Year: Front Neural Circuits. 2008; 2: 5.
DOI: 10.3389/neuro.04.005.2008

Calibration of dynamic holographic optical tweezers for force measurements on biomaterials

Author(s): Astrid van der Horst and Nancy R. Forde

Abstract:

“Holographic optical tweezers (HOTs) enable the manipulation of multiple traps independently in three dimensions in real time. Application of this technique to force measurements requires calibration of trap stiffness and its position dependence. Here, we determine the trap stiffness of HOTs as they are steered in two dimensions. To do this, we trap a single particle in a multiple-trap configuration and analyze the power spectrum of the laser deflection on a position-sensitive photodiode. With this method, the relative trap strengths can be determined independent of exact particle size, and high stiffnesses can be probed because of the high bandwidth of the photodiode. We find a trap stiffness for each of three HOT traps of ? ~26 pN/µm per 100 mW of laser power. Importantly, we find that this stiffness remains constant within ± 4% over 20µm displacements of a trap. We also investigate the minimum step size achievable when steering a trap with HOTs, and find that traps can be stepped and detected within ~2 nm i our instrument, although there is an underlying position modulation of the traps of comparable scale that arises from SLM addressing. The independence of trap stiffness on steering angle over wide ranges and the nanometer positioning accuracy of HOTs demonstrate the applicability of this technique to quantitative study of force response of extended biomaterials such as cells or elastomeric protein networks.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 25, pp. 20987-21003
DOI: 10.1364/OE.16.020987

Phase Contrast Projection Display Using Photopolymer

Author(s): Piao, Mei-Lan; Kim, Nam; Park, Jae-Hyeung

Abstract:

“We propose a phase contrast filter using photopolymer, for the phase contrast projection display. The photopolymer has high photosensitivity such that its optically induced refractive index change has a linear dependency on the illuminating light intensity. We implemented a phase contrast projection display using photopolymer as a phase contrast filter. By controlling the refractive index change of the photopolymer, we successfully convert an input phase image into a high contrast intensity image. We also investigated the effect of the photopolymer illumination condition on the quality of the displayed intensity image. As a projector, we achieved 82% phase to intensity conversion efficiency, which implies that the proposed method can potentially have much higher light efficiency than conventional projection display.”

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Publication: Journal of the Optical Society of Korea
Issue/Year: Journal of the Optical Society of Korea, Volume 12, Issue 4, December 2008, pp.319-325
DOI: 10.3807/JOSK.2008.12.4.319

Phase contrast microscopy with full numerical aperture illumination

Author(s): Christian Maurer, Alexander Jesacher, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“A modification of the phase contrast method in microscopy is presented, which reduces inherent artifacts and improves the spatial resolution. In standard Zernike phase contrast microscopy the illumination is achieved through an annular ring aperture, and the phase filtering operation is performed by a corresponding phase ring in the back focal plane of the objective. The Zernike method increases the spatial resolution as compared to plane wave illumination, but it also produces artifacts, such as the halo- and the shade-off effect. Our modification consists in replacing the illumination ring by a set of point apertures which are randomly distributed over the whole aperture of the condenser, and in replacing the Zernike phase ring by a matched set of point-like phase shifters in the back focal plane of the objective. Experimentally this is done by illuminating the sample with light diffracted from a phase hologram displayed at a spatial light modulator (SLM). The subsequent filtering operation is then done with a second matched phase hologram displayed at another SLM in a Fourier plane of the imaging pathway. This method significantly reduces the haloand shade-off artifacts whilst providing the full spatial resolution of the microscope.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 24, pp. 19821-19829
DOI: 10.1364/OE.16.019821

Generation of laser-induced cavitation bubbles with a digital hologram

Author(s): P. A. Quinto-Su, V. Venugopalan, and C.-D. Ohl

Abstract:

“We demonstrate a method using a spatial light modulator (SLM) to generate arbitrary 2-D spatial configurations of laser induced cavitation bubbles. The SLM acts as a phase hologram that controls the light distribution in the focal plane of a microscope objective. We generate cavitation bubbles over an area of 380×380 µm² with a 20x microscope objective through absorption of the pulsed laser light in a liquid ink solution. We demonstrate the ability to accurately position up to 34 micrometer sized bubbles using laser energies of 56 µJ.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 23, pp. 18964-18969
DOI: 10.1364/OE.16.018964

Dynamic control of higher-order modes in hollow-core photonic crystal fibers

Author(s): T. G. Euser, G. Whyte, M. Scharrer, J. S. Y. Chen, A. Abdolvand, J. Nold, C. F. Kaminski, and P. St. J. Russell

Abstract:

“We present a versatile method for selective mode coupling into higher-order modes of photonic crystal fibers, using holograms electronically generated by a spatial light modulator. The method enables non-mechanical and completely repeatable changes in the coupling conditions. We have excited higher order modes up to LP31 in hollow-core photonic crystal fibers. The reproducibility of the coupling allows direct comparison of the losses of different guided modes in both hollow-core bandgap and kagome-lattice photonic crystal fibers. Our results are also relevant to applications in which the intensity distribution of the light inside the fiber is important, such as particle- or atom-guidance. ”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 22, pp. 17972-17981
DOI: 10.1364/OE.16.017972

Time fluctuations of the phase modulation in a liquid crystal on silicon display: characterization and effects in diffractive optics

Author(s): I. Moreno, A. Lizana, A. Márquez, C. Iemmi, E. Fernández, J. Campos, and M. J. Yzuel

Abstract:

“In this paper we provide evidence of the temporal fluctuations of the phase modulation property of a liquid crystal on silicon (LCoS) display, and we analyze its effect when the device is used for displaying a diffractive optical element. We use a commercial twisted nematic LCoS display configured to produce a phase-only modulation, and we provide time resolved measurements of the diffraction efficiency that show rapid fluctuations of the phase modulation, in the millisecond order. We analyze how these fluctuations have to be considered in two typical methods for the characterization of the phase modulation: two beam interference and diffraction from a binary grating. We finally provide experimental results on the use of this device for displaying a computer generated hologram. A reduction of the modulation diffraction efficiency results from the phase modulation fluctuation.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 21, pp. 16711-16722 (2008)
DOI: 10.1364/OE.16.016711

A spatial light phase modulator with an effective resolution of 4 mega-pixels

Author(s): Daryl Preece; Eric Yao; Graham Gibson; Richard Bowman; Jonathan Leach; Miles Padgett

Abstract:

“We report the design, construction and characterization of a 4 mega-pixel, optically-addressed, spatial light modulator (OSLM). The intensity distribution corresponding to a kinoform is displayed across two wide-screen liquid crystal on silicon displays, the images of which are combined and relayed to the address face of a 40 mm aperture OSLM. This spatially varying intensity profile is converted into a phase hologram on the readout side of the OSLM. When illuminated at 532 nm we measure a first-order diffraction efficiency of ≈50% at 400 line pairs and ≈20% at 900 line pairs. We show that aberration associated with the non-flatness of the device can be corrected within software by modification of the hologram.”

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Publication: Journal of Modern Optics
Issue/Year: Journal of Modern Optics, Volume 55, Issue 18 October 2008 , pages 2945 – 2951
DOI: 10.1080/09500340802272357

Three-dimensional parallel holographic micropatterning using a spatial light modulator

Author(s): Nathan J. Jenness, Kurt D. Wulff, Matthew S. Johannes, Miles J. Padgett, Daniel G. Cole, and Robert L. Clark

Abstract:

“We present a micropatterning method for the automatic transfer and arbitrary positioning of computer-generated three-dimensional structures within a substrate. The Gerchberg-Saxton algorithm and an electrically addressed spatial light modulator (SLM) are used to create and display phase holograms, respectively. A holographic approach to light manipulation enables arbitrary and efficient parallel photo-patterning. Multiple pyramidal microstructures were created simultaneously in a photosensitive adhesive. A scanning electron microscope was used to confirm successful replication of the desired microscale structures. ”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 20, pp. 15942-15948 (2008)
DOI: 10.1364/OE.16.015942

Collisions of Dark Solitons in Elongated Bose-Einstein Condensates

Author(s): S. Stellmer, C. Becker, P. Soltan-Panahi, E.-M. Richter, S. Dörscher, M. Baumert, J. Kronjäger, K. Bongs, and K. Sengstock

Abstract:

“We present experimental data showing the head-on collision of dark solitons generated in an elongated Bose-Einstein condensate. No discernable interaction can be recorded, in full agreement with the fundamental theoretical concepts of solitons as mutually transparent quasiparticles. Our soliton generation technique allows for the creation of solitons with different depths; hence, they can be distinguished and their trajectories be followed. Simulations of the 1D-Gross-Pitaevskii equation have been performed to compare the experiment with a mean-field description.”

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Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett. 101, Issue 12, 120406 (2008)
DOI: 10.1103/PhysRevLett.101.120406
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