New microscopy technique based on position localization of scattering particles

Author(s):

Stefano Luigi Oscurato and Fabio Borbone and Robert Charles Devlin and Federico Capasso and Pasqualino Maddalena and Antonio Ambrosio

Abstract:

“We introduce the Holographic – Single Scatterer Localization Microscopy in which we combine dynamical laser speckle illumination with centroid localization of backscattered light spots in order to localize isolated scattering particles. The reconstructed centroid images show very accurate particle localization, with precision much better than the width of diffraction-limited image of the particles recorded by the CCD. Furthermore, the method provides an improved resolution in distinguishing two very close scattering objects compared to the standard laser scanning techniques and can be assimilated to a confocal technique in the ability of light background rejection in three-dimensional disposition of scattering objects. The illumination is controlled via a digital holography setup based on the use of a spatial light modulator. This allows not only a high level of versatility in the illumination patterns, but also the remarkable characteristics of absence of moving mechanical parts, typical of the laser scanning techniques, and the possibility of strongly miniaturizing the setup.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express Vol. 25, Issue 10, pp. 11530-11549 (2017)

DOI: 10.1364/OE.25.011530

 

Diffraction-free light droplets for axially-resolved volume imaging.

Author(s):

Antonacci, G. and Domenico, G. Di and Silvestri, S. and DelRe, E. and Ruocco, G.

Abstract:

“An ideal direct imaging system entails a method to illuminate on command a single diffraction-limited region in a generally thick and turbid volume. The best approximation to this is the use of large-aperture lenses that focus light into a spot. This strategy fails for regions that are embedded deep into the sample, where diffraction and scattering prevail. Airy beams and Bessel beams are solutions of the Helmholtz Equation that are both non-diffracting and self-healing, features that make them naturally able to outdo the effects of distance into the volume but intrinsically do not allow resolution along the propagation axis. Here, we demonstrate diffraction-free self-healing three-dimensional monochromatic light spots able to penetrate deep into the volume of a sample, resist against deflection in turbid environments, and offer axial resolution comparable to that of Gaussian beams. The fields, formed from coherent mixtures of Bessel beams, manifest a more than ten-fold increase in their undistorted penetration, even in turbid milk solutions, compared to diffraction-limited beams. In a fluorescence imaging scheme, we find a ten-fold increase in image contrast compared to diffraction-limited illuminations, and a constant axial resolution even after four Rayleigh lengths. Results pave the way to new opportunities in three-dimensional microscopy.”

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Publication: Scientific Reports

Issue/Year/DOI: Scientific Reports volume 7, Article number: 17 (2017)
DOI: 10.1038/s41598-017-00042-w

Far-field imaging of non-fluorescent species with subdiffraction resolution

Author(s):

Wang, Pu, and Mikhail N. Slipchenko, and James Mitchell, and Chen Yang, and Eric O. Potma, and Xianfan Xu, and Ji-Xin Cheng

Abstract:

“Super-resolution optical microscopy is providing a new means by which to view as yet unseen details on a nanoscopic scale. Current far-field super-resolution techniques rely on fluorescence as the readout1–5.
Here, we demonstrate a scheme for breaking the diffraction limit in far-field imaging of nonfluorescent species by using spatially controlled saturation of electronic absorption. Our method is based on a pump–probe process where a modulated pump field perturbs the charge carrier density in a sample, thus modulating the transmission of a probe field. A doughnut-shaped laser beam is then added to transiently saturate the electronic transition in the periphery of the focal volume, so the induced modulation in the sequential probe pulse only occurs at the focal centre. By raster-scanning the three collinearly aligned beams, high-speed subdiffractionlimitedimaging of graphite nanoplatelets is performed. This technique has the potential to enable super-resolution imaging of nanomaterials and non-fluorescent chromophores, which may remain out of reach to fluorescence-based methods.”

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Publication: NATURE PHOTONICS ADVANCE ONLINE PUBLICATION

Issue/Year/DOI: Nature Photonics volume 7, pages 449–453 (2013)
DOI: 10.1038/NPHOTON.2013.97

Double peacock eye optical element for extended focal depth imaging with ophthalmic applications

Author(s): Lenny A. Romero, María S. Millán, Zbigniew Jaroszewicz, Andrzej Kolodziejczyk.

Abstract:

“The aged human eye is commonly affected by presbyopia, and therefore, it gradually loses its capability to form images of objects placed at different distances. Extended depth of focus (EDOF) imaging elements can overcome this inability, despite the introduction of a certain amount of aberration. This paper evaluates the EDOF imaging performance of the so-called peacock eye phase diffractive element, which focuses an incident plane wave into a segment of the optical axis and explores the element’s potential use for ophthalmic presbyopia compensation optics. Two designs of the element are analyzed: the single peacock eye, which produces one focal segment along the axis, and the double peacock eye, which is a spatially multiplexed element that produces two focal segments with partial overlapping along the axis. The performances of the peacock eye elements are compared with those of multifocal lenses through numerical simulations as well as optical experiments in the image space. The results demonstrate that the peacock eye elements form sharper images along the focal segment than the multifocal lenses and, therefore, are more suitable for presbyopia compensation. The extreme points of the depth of field in the object space, which represent the remote and the near object points, have been experimentally obtained for both the single and the double peacock eye optical elements. The double peacock eye element has better imaging quality for relatively short and intermediate distances than the single peacock eye, whereas the latter seems better for far distance vision.”

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Publication: Journal of Biomedical Optics , (subscription required)

Issue/Year/DOI: J. Biomed. Opt. 17, 046013 (Apr 27, 2012)
doi:10.1117/1.JBO.17.4.046013

Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination

Author(s): Antonio Ambrosio, Lorenzo Marrucci, Fabio Borbone, Antonio Roviello, Pasqualino Maddalena

Abstract:

“When an azobenzene-containing polymer film is exposed to a non-uniform illumination, a light-induced mass migration process may be induced, leading to the formation of relief patterns on the polymer free surface. Despite a research effort of many years and several proposed models many aspects of this phenomenon remain not well understood. Here we report the appearance of spiral-shaped relief patterns on the polymer under the illumination of focused Laguerre-Gauss beams, having helical wavefront and an optical vortex at their axis. The induced spiral reliefs are sensitive to the vortex topological charge and to the wavefront handedness. These findings are unexpected, because the “doughnut”-shaped intensity profile of Laguerre- Gauss beams contains no information about the wavefront handedness. We propose a model that explains the main features of this phenomenon from the surface-mediated interference of the longitudinal and the transverse components of the optical field. These results may find applications in optical micro- and nanolithography and optical-field. ”

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Publication: eprint arXiv:1203.5205, (free download)

Issue/Year/DOI: eprint arXiv:1203.5205 (2012)
Bibliographic Code: 2012arXiv1203.5205A

Three dimensional optical twisters-driven helically stacked multi-layered microrotors

Author(s): Jolly Xavier, Raktim Dasgupta, Sunita Ahlawat, Joby Joseph, and Pradeep Kumar Gupta

Abstract:

“We demonstrate tunable helically stacked multi-layered microrotors realized in vortex-embedded three dimensional (3D) optical twister patterns. Intensity-tunable annular irradiance profiles with higher order vortex are generated as well as simultaneously unfolded by phase-engineered multiple plane wave interference. In the individually tunable 3D helical bright arms of these unfolded vortex structures, 2 μm silica beads are optically trapped as spiraling multilayered handles of multi-armed microrotors. Further, multiple rows of such microrotors are parallelly actuated with controllable sense of rotation. We also present our observation on helical 3D stacking of micro-particles in these longitudinally gyrating multi-armed rotor traps.”

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Publication: Applied Physics Letters, (subscription required)

Issue/Year/DOI: Applied Physics Letters, Volume 100, Issue 12, (2012)
doi:10.1063/1.3693413

Vertical differential interference contrast

Author(s): Michael Warber, Tobias Haist, Malte Hasler, and Wolfgang Osten

Abstract:

“We propose a new phase contrast filtering technique based on a combination of a focused and a defocused point-spread-function. This way, an axial shear is introduced in the imaging system. Compared to conventional differential interference contrast, an isotropic behavior is achieved. The lateral resolution is improved compared to conventional defocusing. Furthermore, the digital combination of multiple images leads to strongly enhanced visualization of small structures. We show simulated results as well as experimental results using a spatial-light modulator-based microscope.”

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Publication: Optical Engineering, (subscription required)

Issue/Year/DOI: Opt. Eng., Volume 51, Issue 1, 013204, (2012)
doi:10.1117/1.OE.51.1.013204

Scattered light fluorescence microscopy in three dimensions

Author(s): Giulia Ghielmetti and Christof M. Aegerter

Abstract:

“Recently, we have proposed a method to image fluorescent structures behind turbid layers at diffraction limited resolution using wave-front shaping and the memory effect. However, this was limited to a raster scanning of the wave-front shaped focus to a two dimensional plane. In applications, it can however be of great importance to be able to scan a three dimensional volume. Here we show that this can be implemented in the same setup. This is achieved by the addition of a parabolic phase shift to the shaped wave-front. Via the memory effect, this phase shift leads to a shift of the interference based focus in the z-direction, thus opening the possibility of three dimensional imaging using scattered light fluorescence microscopy. Here, we show an example of such a three dimensional image of fluorescent nano-beads taken behind a turbid layer more than 10 mean free paths thick. Finally, we discuss the differences of the scanning in the z-direction with that in the x–y plane and the corresponding possibilities and limitations of the technique.”

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Publication: Optics Express, (free download)

Issue/Year/DOI: Optics Express, Vol. 20, Issue 4, pp. 3744-3752 (2012)
doi:10.1364/OE.20.003744

Positional stability of holographic optical traps

Author(s): Arnau Farré, Marjan Shayegan, Carol López-Quesada, Gerhard A. Blab, Mario Montes-Usategui, Nancy R. Forde, and Estela Martín-Badosa

Abstract:

“The potential of digital holography for complex manipulation of micron-sized particles with optical tweezers has been clearly demonstrated. By contrast, its use in quantitative experiments has been rather limited, partly due to fluctuations introduced by the spatial light modulator (SLM) that displays the kinoforms. This is an important issue when high temporal or spatial stability is a concern. We have investigated the performance of both an analog-addressed and a digitally-addressed SLM, measuring the phase fluctuations of the modulated beam and evaluating the resulting positional stability of a holographic trap. We show that, despite imparting a more unstable modulation to the wavefront, our digitally-addressed SLM generates optical traps in the sample plane stable enough for most applications. We further show that traps produced by the analog-addressed SLM exhibit a superior pointing stability, better than 1 nm, which is comparable to that of non-holographic tweezers. These results suggest a means to implement precision force measurement experiments with holographic optical tweezers (HOTs).”

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Publication: Optics Express, (free download)

Issue/Year/DOI: Optics Express, Vol. 19, Issue 22, pp. 21370-21384 (2011)
doi:10.1364/OE.19.021370

Controlling ghost traps in holographic optical tweezers

Author(s): Christina Hesseling, Mike Woerdemann, Andreas Hermerschmidt, Cornelia Denz.

Abstract:

“Computer-generated holograms displayed by phase-modulating spatial light modulators have become a well- established tool for beam shaping purposes in holographic optical tweezers. Still, the generation of light intensity patterns with high spatial symmetry and simultaneously without interfering ghost traps is a challenge. We have implemented an iterative Fourier transform algorithm that is capable of controlling these ghost traps and demonstrate the benefit of this approach in the experiment.”

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Publication: Optics Letters, (subscription required)

Issue/Year/DOI: Optics Letters, Vol. 36, Issue 18, pp. 3657-3659 (2011)
doi:10.1364/OL.36.003657