Generation of composite vortex beams by independent Spatial Light Modulator pixel addressing

Author(s):

Mateusz Szatkowski, Jan Masajada, Ireneusz Augustyniak and Klaudia Nowacka

Abstract:

“The composite optical beams being a result of superposition, are a promising way to study the orbital angular momentum and its effects. Their wide range of applications makes them attractive and easily available due to the growing interest in the Spatial Light Modulators (SLM). In this paper, we present a simple method for generating composite vortex patterns with high symmetry. Our method is simple, flexible and gives perfectly aligned beams, insensitive to mechanical vibrations. This method is based on the ability to split SLM cells between phase patterns that are to be superposed. This approach allows control of the intensity relation between those structures, enables their rotation and is capable to superpose more than two such structures.
In this paper, we examine its ability to produce superposition of two optical vortices by presenting both theoretical and experimental results. ”

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Publication: Optics Communications

Issue/Year/DOI: Volume 463
DOI: 10.1016/j.optcom.2020.125341

Amplitude-phase optimized long depth of focus femtosecond axilens beam for single-exposure fabrication of high-aspect-ratio microstructures

Author(s):

Deng Pan, Bing Xu, Shunli Liu, Jiawen Li, Yanlei Hu, Dong Wu, and Jiaru Chu

Abstract:

“Fabrication of high-aspect-ratio (HAR) micro/nanostructures by two-photon polymerization (TPP) has become a hot topic because of the advantages of ultra-high resolution and true 3D printing ability. However, the low efficiency caused by point-by-point scanning strategy limits its application. In this Letter, we propose a strategy for the rapid fabrication of HAR microstructures by combining TPP with an amplitude-phase optimized long depth of focus laser beam (LDFB). The optimization of the LDFB is implemented by modulating the amplitude and phase on a phase-only spatial light modulator, which can suppress the side lobe and smooth energy oscillations effectively. The LDFB is used for rapid fabrication of HAR micropillars and various microstructures, which greatly increases the fabrication efficiency. As a demonstration, several typical HAR microstructures such as assemblies, microchannels, microtubes, and cell scaffolds are prepared. Moreover, the microcapture arrays are rapidly fabricated for the capture of microspheres and the formation of microlens arrays, which show focusing and imaging ability.”

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Publication: Optics Letters
Issue/Year/DOI: Vol. 45, Issue 9, pp. 2584-2587 (2020)
DOI: 10.1364/OL.389946

Three-dimensional laser damage positioning by a deep-learning method

Author(s):

Zhan Li and Lu Han and Xiaoping Ouyang and Pan Zhang and Yajing Guo and Dean Liu and Jianqiang Zhu

Abstract:

“A holographic and deep learning-based method is presented for three-dimensional
laser damage location. The axial damage position is obtained by numerically focusing the
diffraction ring into the conjugate position. A neural network Diffraction-Net is proposed to
distinguish the diffraction ring from different surfaces and positions and obtain the lateral position.
Diffraction-Net, which is completely trained by simulative data, can distinguish the diffraction
rings with an overlap rate greater than 61% which is the best of results reported. In experiments,
the proposed method first achieves the damage pointing on each surface of cascade slabs using
diffraction rings, and the smallest inspect damage size is 8μm. A high precision result with the
lateral positioning error less than 38.5μm and axial positioning error less than 2.85mm illustrates
the practicability for locating the damage sites at online damage inspection.”

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Publication: Optics Express
Issue/Year/DOI: Vol. 28, Issue 7, pp. 10165-10178
DOI: 10.1364/OE.387987

Three-dimensional tomography of red blood cells using deep learning

Author(s):

Joowon Lim and Ahmed B. Ayoub and Demetri Psaltis

Abstract:

“We accurately reconstruct three-dimensional (3-D) refractive index (RI) distributions from highly
ill-posed two-dimensional (2-D) measurements using a deep neural network (DNN). Strong distortions are
introduced on reconstructions obtained by the Wolf transform inversion method due to the ill-posed
measurements acquired from the limited numerical apertures (NAs) of the optical system. Despite the
recent success of DNNs in solving ill-posed inverse problems, the application to 3-D optical imaging is
particularly challenging due to the lack of the ground truth. We overcome this limitation by generating
digital phantoms that serve as samples for the discrete dipole approximation (DDA) to generate multiple
2-D projection maps for a limited range of illumination angles. The presented samples are red blood cells
(RBCs), which are highly affected by the ill-posed problems due to their morphology. The trained network
using synthetic measurements from the digital phantoms successfully eliminates the introduced distortions.
Most importantly, we obtain high fidelity reconstructions from experimentally recorded projections of real RBC
sample using the network that was trained on digitally generated RBC phantoms. Finally, we confirm the
reconstruction accuracy using the DDA to calculate the 2-D projections of the 3-D reconstructions and
compare them to the experimentally recorded projections.”

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Publication: Advanced Photonics
Issue/Year/DOI: Vol. 2, Issues 2
DOI: 10.1117/1.AP.2.2.026001

Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers

Author(s):

Eileen Otte, Kemal Tekce, Sebastian Lamping, Bart Jan Ravoo and Cornelia Denz
Abstract:

“Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.”

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Publication: Nature Communications
Issue/Year/DOI: Nature Communications volume 10, Article number: 4308 (2019)
DOI: 10.1038/s41467-019-12127-3

Chain of optical vortices synthesized by a Gaussian beam and the double-phase-ramp converter

Author(s):

Anna Khoroshun, Oleksii Chernykh, Halyna Tatarchenko, Shunichi Sato, Yuichi Kozawa, Agnieszka Popiołek-Masajada, Mateusz Szatkowski, and Weronika Lamperskan

Abstract:

“A full theoretical and experimental analysis of the chain of phase singularities generated when a Gaussian beam passes a double-phase-ramp converter is presented. The overall output beam structure includes a system of interrelated optical vortices (OVs) whose trajectories form a three-dimensional singular skeleton that can be applied for the trapping and guiding of microparticles. The internal structure of each individual phase singularity is characterized by the OV topological charge and by the morphology parameters of equal intensity ellipses in the OV-core area: ellipticity (minor-to-major axes ratio) and the inclination angle. The morphology parameters’ evolution is shown to be valuable for the metrology applications.”

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Publication: OSA Continuum
Issue/Year/DOI: Vol. 2, Issue 2, pp. 320-331 (2019)
DOI: 10.1364/OSAC.2.000320

Measuring orbital angular momentums of light based on petal interference patterns

Author(s):

Shengzhe Pan and Chunying Pei and Shuang Liu and Jin Wei and Di Wu and Zhanou Liu and Yaling Yin and Yong Xia and Jianping Yin

Abstract:

“We demonstrate an interferometric method to measure the topological charges of the vortex beams carrying orbital angular momentums (OAMs). The petal interference patterns are generated by combining modulated vortex beams and an unmodulated incident Gaussian beam reflected by a spatial light modulator. The number of petals is in agreement with the value of OAM that the modulated beam carries, by which we analyze the characteristic of interference patterns of integer OAM beams, including intensity profiles, phase profiles, and hologram structures. We also uncover the principle of how radial parameter l influences the hollow radius of OAM beams. Beams carrying non-integer orbital angular momentums are visualized with our method, from which we observe the evolution of a speckle generated by the decimal part of holograms. A kind of hologram is designed to prove that the petal near the singularity line is separated owing to the diffraction enhancement. All the experiment results agree well with the simulated results.”

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Publication: OSA Continuum
Issue/Year/DOI: OSA Continuum Volume 1, Issue 2 (2018)
DOI: 10.1364/OSAC.1.000451

Laser surface structuring of diamond with ultrashort Bessel beams

Author(s):

Sanjeev Kumar, Shane M. Eaton, Monica Bollani, Belén Sotillo, Andrea Chiappini, Maurizio Ferrari, Roberta Ramponi, Paolo Di Trapani, Ottavia Jedrkiewicz

Abstract:

“We investigate the effect of ultrafast laser surface machining on a monocrystalline synthetic diamond sample by means of pulsed Bessel beams. We discuss the differences of the trench-like microstructures generated in various experimental conditions, by varying the beam cone angle, the energy and pulse duration, and we present a brief comparison of the results with those obtained with the same technique on a sapphire sample. In diamond, we obtain V-shaped trenches whose surface width varies with the cone angle, and which are featured by micrometer sized channels having depths in the range of 10–20 μm. By laser writing crossed trenches we are also able to create and tailor on the diamond surface pillar-like or tip-like microstructures potentially interesting for large surface functionalization, cells capturing and biosensing.”

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Publication: Scientific Reports

Issue/Year/DOI: Scientific Reports 8, Article number: 14021 (2018)

DOI: 10.1038/s41598-018-32415-0

Generation of elliptic perfect optical vortex and elliptic perfect vector beam by modulating the dynamic and geometric phase

Author(s):

Delin Li and Chenliang Chang and Shouping Nie and Shaotong Feng and Jun Ma and Caojin Yuan

Abstract:

“We propose a method for generating an elliptic perfect vector beam (EPVB) by modulating the dynamic and geometric phases. It is theoretically demonstrated that the shape of the beam can be changed from circle to ellipse by setting the scale factor m of the dynamic phase, but the diameter of it is independent on the topological charge and the polarization order. Since the geometric phases provided by the dialectic Q-plate vary with the polarization state of the illumination beam, EPVB can be converted to the elliptic perfect optical vortex (EPOV) beam by changing the polarization state of the illuminating beam. Therefore, we also provide an alternative method to generate the EPOV beam. The experimental results agree well with the theoretical expectations.”

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Publication: Applied Physics Letters
Issue/Year/DOI: Applied Physics Letters Volume 113, Issue 12

DOI: 10.1063/1.5048327

Nonlinear generation of Airy vortex beam

Author(s):
Hui Li and Haigang Liu and Xianfeng Chen

Abstract:

“Recently, hybrid beams have sparked considerable interest because of their properties coming from different kinds of beams at the same time. Here, we experimentally demonstrate Airy vortex beam generation in the nonlinear frequency conversion process when the fundamental wave with its phase modulated by a spatial light modulator is incident into a homogeneous nonlinear medium. In our experiments, second harmonic Airy circle vortex beams and Airy ellipse vortex beams were generated and the topological charge was also measured. The parabolic trajectory of those Airy vortex beams can be easily adjusted by altering the fundamental wave phase. This study provides a simple way to generate second harmonic Airy vortex beams, which may broaden its future use in optical manipulation and light-sheet microscopy.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express Volume 26, Issue 16
DOI: 10.1364/oe.26.021204

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