Lateral position correction in ptychography using the gradient of intensity patterns

Author(s):

Priya Dwivedi and Sander Konijnenberg and Silvania Pereira and Paul Urbach

Abstract:

“Ptychography, a form of Coherent Diffractive Imaging, is used with short wavelengths (e.g. X-rays, electron beams) to achieve high-resolution image reconstructions. One of the limiting factors for the reconstruction quality is the accurate knowledge of the illumination probe positions. Recently, many advances have been made to relax the requirement for the probe positions accuracy. Here, we analyse and demonstrate a straightforward approach that can be used to correct the probe positions with sub-pixel accuracy. Simulations and experimental results with visible light are presented in this work.”

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Publication: Ultramicroscopy

Issue/Year/DOI: Ultramicroscopy, Volume 192, September 2018, Pages 29-36
DOI: 10.1016/j.ultramic.2018.04.004

Generation of focal pattern with controllable polarization and intensity for laser beam passing through a multi-mode fiber

Author(s):

Weiru Fan and Xiansheng Hu and Bamao Zhaxi and Ziyang Chen and Jixiong Pu

Abstract:

“Similar to coherent light passing through a scattering medium, the propagation of coherent light through a multi-mode fiber (MMF) will result in a random speckle field. For a non-polarization maintaining MMF, the randomization can be observed not only in the intensity distribution, but also in the polarization state. In this paper, we propose a new technique known as phase combination to control the optical field for the light passing through the MMF. We show that, based on this new technique, the random speckle pattern can be modulated into an intensity distribution of two bright focal spots with mutually perpendicular polarization by only one polarizer. In particular, the intensity distribution of these two focal spots can be quantitatively controlled. This technique may find applications in medical imaging, nonlinear optics and optical communication etc.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express Vol. 26, Issue 6, pp. 7693-7700 (2018)
DOI: 10.1364/OE.26.007693

Tunable third harmonic generation of vortex beams in an optical superlattice

Author(s):

Yu Wu and Rui Ni and Zhou Xu and Yaodong Wu and Xinyuan Fang and Dan Wei and Xiaopeng Hu and Yong Zhang and Min Xiao and Shining Zhu

Abstract:

“We report generation of tunable vortex beams in the blue spectral range, with a 3.3 nm spectral tuning range, by frequency tripling of the near-infrared (IR) wave at around 1.34 um in a LiTaO3 optical superlattice. The nonlinear crystal used in this work has a chirped dual-periodical structure which can provide two expanded reciprocal vectors for tunable performance of the cascaded third harmonic generation (THG). The maximum THG efficiency reaches about 1.4%.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express, Vol. 25, Issue 25, pp. 30820- 30826 (2017)
DOI: 10.1364/OE.25.030820

Silver Nanowires for Reconfigurable Bloch Surface Waves.

Author(s):

Zhang, Douguo and Wang, Ruxue and Xiang, Yifeng and Kuai, Yan and Kuang, Cuifang and Badugu, Ramachandram and Xu, Yingke and Wang, Pei and Ming, Hai and Liu, Xu and Lakowicz, Joseph R.

Abstract:

“The use of a single silver nanowire as a flexible coupler to transform a free space beam into a Bloch surface wave propagating on a dielectric multilayer is proposed. Based on Huygens ‘Principle, when a Gaussian beam is focused onto a straight silver nanowire, a Bloch surface wave is generated and propagates perpendicular to the nanowire. By curving the silver nanowire, the surface wave can be focused. Furthermore, the spatial phase of the incident laser beam can be actively controlled with the aid of a spatial light modulator, resulting in the reconfigurable or dynamically controlled Bloch surface waves. The low cost of the chemically synthesized silver nanowires and the high flexibility with regard to tuning the spatial phase of the incident light make this approach very promising for various applications including optical micromanipulation, fluorescence imaging, and sensing.”

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Publication: ACS Nano

Issue/Year/DOI:  ACS Nano, 2017, 11 (10), pp 10446–10451
DOI: 10.1021/acsnano.7b05638

Miniature wide-spectrum mode sorter for vortex beams produced by 3D laser printing

Author(s):

Shlomi Lightman and Gilad Hurvitz and Raz Gvishi and Ady Arie

Abstract:

“Optical vortex beams can be used as carriers of information in optical communication and quantum optics applications. Owing to their spatial orthogonality, these beams can be multiplexed and demultiplexed, but up until now this was primarily achieved by bulky and large devices. In this work, a new approach is used to fabricate miniature vortex mode sorters based on three-dimensional laser printing, thereby enabling direct integration into optical systems. Mode sorters that are composed of two separate elements as well as a single integrated device are presented. These devices can handle both pure and mixed vortex beams with topological charge |𝑙|3 and |𝑙|2 for the dual-element device and integrated system, respectively. Mode-sorter spectral bandwidth and surface-quality effects are also discussed.”

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Publication: Optica

Issue/Year/DOI: Optica, Vol 4. , Issue 6, pp. 605- 610 (2018)
DOI: 10.1364/OPTICA.4.000605

Plasmonic computing of spatial differentiation.

Author(s):

Zhu, Tengfeng and Zhou, Yihan and Lou, Yijie and Ye, Hui and Qiu, Min and Ruan, Zhichao and Fan, Shanhui

Abstract:

“Optical analog computing offers high-throughput low-power-consumption operation for specialized computational tasks. Traditionally, optical analog computing in the spatial domain uses a bulky system of lenses and filters. Recent developments in metamaterials enable the miniaturization of such computing elements down to a subwavelength scale. However, the required metamaterial consists of a complex array of meta-atoms, and direct demonstration of image processing is challenging. Here, we show that the interference effects associated with surface plasmon excitations at a single metal-dielectric interface can perform spatial differentiation. And we experimentally demonstrate edge detection of an image without any Fourier lens. This work points to a simple yet powerful mechanism for optical analog computing at the nanoscale.”

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Publication: Nature Communications

Issue/Year/DOI: Nature Communications volume 8, Article number: 15391 (2017)
DOI: 10.1038/ncomms15391

High power, ultrashort pulse control through a multi-core fiber for ablation

Author(s):

Donald B. Conkey and Eirini Kakkava and Thomas Lanvin and Damien Loterie and Nicolino Stasio and Edgar Morales-Delgado and Christophe Moser and Demetri Psaltis

Abstract:

“Ultrashort pulse ablation has become a useful tool for micromachining and biomedical surgical applications. Implementation of ultrashort pulse ablation in confined spaces has been limited by endoscopic delivery and focusing of a high peak power pulse. Here we demonstrate ultrashort pulse ablation through a thin multi-core fiber (MCF) using wavefront shaping, which allows for focusing and scanning the pulse without requiring distal end optics and enables a smaller ablation tool. The intensity necessary for ablation is significantly higher than for multiphoton imaging. We show that the ultimate limitations of the MCF based ablation are the nonlinear effects induced by the pulse in the MCFs cores. We characterize and compare the performance of two devices utilizing a different number of cores and demonstrate ultrashort pulse ablation on a thin film of gold.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express Vol. 25, Issue 10, pp. 11491-11502 (2017)

DOI: 10.1364/OE.25.011491

 

Chromatic aberration control with liquid crystal spatial phase modulators

Author(s):

Jose L. Martinez and Enrique J. Fernandez and Pedro M. Prieto and Pablo Artal

Abstract:

“The chromatic behavior of diffractive optical elements, exhibiting 2π-wrapped phase profiles, implemented into liquid crystal spatial light modulators (LC-SLM) is described. A wrapped phase map is only equivalent to the original continuous profile for the design wavelength while at other wavelengths there are unwanted phase jumps and the profile does not correspond to a pure defocus. For those conditions the wrapped profile behaves as a multiple order lens (multi-focal lens). The optical power dispersion for each order is linearly proportional to the wavelength, while the energy of each order depends on the design wavelength and the material dispersion. For practical purposes, for most of the visible range only first order (main defocus) is relevant but two other orders may also be considered depending on the actual PSF of the system. As an application, we demonstrate that the longitudinal chromatic aberration of the eye can be compensated by the diffractive lens dispersion when the appropriate defocus is programmed into the SLM.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express, Vol. 25, Issue 9, pp. 9793-9801 (2018)
DOI: 10.1364/OE.25.009793

 

Fabrication of three-dimensional electrospun microstructures using phase modulated femtosecond laser pulses

Author(s): Nathan J. Jenness, Yiquan Wu, Robert L. Clark.

Abstract:

“Electrospun polycaprolactone nanofibers were selectively ablated to form microstructures via the phase modulation of femtosecond laser beams. Ablation width (1–15 μm) and depth (15–110 μm) resolution were dependent upon the selection of pulse energy and microscope objective. Because phase modulation shapes light in a maskless fashion, desired templates were digitally created and physically transferred to electrospun mats within a matter of minutes. Several microarchitectures were formed in parallel by dividing pulse energy between multiple foci, substantially increasing throughput. The data presented herein demonstrates that phase-based laser ablation can be used to rapidly shape and tailor electrospun mats in three dimensions.”

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Publication: Materials Letters, (subscription required)

Issue/Year/DOI: Materials Letters, Volume 66, Issue 1, 1 January 2012, Pages 360–363
doi:10.1016/j.matlet.2011.09.015

Binocular adaptive optics vision analyzer with full control over the complex pupil functions

Author(s): Christina Schwarz, Pedro M. Prieto, Enrique J. Fernández, and Pablo Artal

Abstract:

“We present a binocular adaptive optics vision analyzer fully capable of controlling both amplitude and phase of the two complex pupil functions in each eye of the subject. A special feature of the instrument is its comparatively simple setup. A single reflective liquid crystal on silicon spatial light modulator working in pure phase modulation generates the phase profiles for both pupils simultaneously. In addition, another liquid crystal spatial light modulator working in transmission operates in pure intensity modulation to produce a large variety of pupil masks for each eye. Subjects perform visual tasks through any predefined variations of the complex pupil function for both eyes. As an example of the system efficiency, we recorded images of the stimuli through the system as they were projected at the subject’s retina. This instrument proves to be extremely versatile for designing and testing novel ophthalmic elements and simulating visual outcomes, as well as for further research of binocular vision.”

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Publication: Optics Letters, (subscription required)

Issue/Year/DOI: Optics Letters, Vol. 36, Issue 24, pp. 4779-4781 (2011)
doi:10.1364/OL.36.004779

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