Spiral Caustics of Vortex Beams

Author(s):

Soifer, Viktor; Kharitonov, Sergey; Khonina, Svetlana; Strelkov, Yurii & Porfirev, Alexey

Abstract:

“We discuss the nonparaxial focusing of laser light into a three-dimensional (3D) spiral distribution. For calculating the tangential and normal components of the electromagnetic field on a preset curved surface we propose an asymptotic method, using which we derive equations for calculating stationary points and asymptotic relations for the electromagnetic field components in the form of one-dimensional (1D) integrals over a radial component. The results obtained through the asymptotic approach and the direct calculation of the Kirchhoff integral are identical. For a particular case of focusing into a ring, an analytical relation for stationary points is derived. Based on the electromagnetic theory, we design and numerically model the performance of diffractive optical elements (DOEs) to generate field distributions shaped as two-dimensional (2D) and 3D light spirals with the variable angular momentum. We reveal that under certain conditions, there is an effect of splitting the longitudinal electromagnetic field component. Experimental results obtained with the use of a spatial light modulator are in good agreement with the modeling results.”

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Publication: Photonics
Issue/Year: Photonics, Volume 8; Number 1; Pages 24; 2021
DOI: 10.3390/photonics8010024

Swallowtail-type diffraction catastrophe beams

Author(s):

Teng, Houan; Qian, Yixian; Lan, Yanping & Cui, Wentao

Abstract:

“We demonstrate a universal approach for generating high-order diffraction catastrophe beams, specifically for Swallowtail-type beams (abbreviated as Swallowtail beams), using diffraction catastrophe theory that was defined by potential functions depending on the control and state parameters. The three-dimensional curved caustic surfaces of these Swallowtail catastrophe beams are derived by the potential functions. Such beams are generated by mapping the cross sections of the high-order control parameter space to the corresponding transverse plane. Owing to the flexibility of the high-order diffraction catastrophe, these Swallowtail beams can be tuned to a diverse range of optical light structures. Owing to the similarity in their frequency spectra, we found that the Swallowtail beams change into low-order Pearcey beams under given conditions during propagation. Our experimental results are in close agreement with our simulated results. Such fantastic catastrophe beams that can propagate along curved trajectories are likely to give rise to new applications in micromachining and optical manipulation, furthermore, these diverse caustic beams will pave the way for the tailoring of arbitrarily accelerating caustic beams.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 3; Pages 3786; 2021
DOI: 10.1364/oe.416134

Zeroth- and first-order long range non-diffracting GausstextendashBessel beams generated by annihilating multiple-charged optical vortices

Author(s):

Stoyanov, Lyubomir; Zhekova, Maya; Stefanov, Aleksander; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“We demonstrate an alternative approach for generating zeroth- and first-order long range non-diffracting Gauss–Bessel beams (GBBs). Starting from a Gaussian beam, the key point is the creation of a bright ring-shaped beam with a large radius-to-width ratio, which is subsequently Fourier-transformed by a thin lens. The phase profile required for creating zeroth-order GBBs is flat and helical for first-order GBBs with unit topological charge (TC). Both the ring-shaped beam and the required phase profile can be realized by creating highly charged optical vortices by a spatial light modulator and annihilating them by using a second modulator of the same type. The generated long-range GBBs are proven to have negligible transverse evolution up to 2 m and can be regarded as non-diffracting. The influences of the charge state of the TCs, the propagation distance behind the focusing lens, and the GBB profiles on the relative intensities of the peak/rings are discussed. The method is much more efficient as compared to this using annular slits in the back focal plane of lenses. Moreover, at large propagation distances the quality of the generated GBBs significantly surpasses this of GBBs created by low angle axicons. The developed analytical model reproduces the experimental data. The presented method is flexible, easily realizable by using a spatial light modulator, does not require any special optical elements and, thus, is accessible in many laboratories.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-78613-7

Gigantic vortical differential scattering as a monochromatic probe for multiscale chiral structures

Author(s):

Ni, Jincheng; Liu, Shunli; Wu, Dong; Lao, Zhaoxin; Wang, Zhongyu; Huang, Kun; Ji, Shengyun; Li, Jiawen; Huang, Zhixiang; Xiong, Qihua; Hu, Yanlei; Chu, Jiaru & Qiu, Cheng-Wei

Abstract:

“Spin angular momentum of light is vital to investigate enantiomers characterized by circular dichroism (CD), widely adopted in biology, chemistry, and material science. However, to discriminate chiral materials with multiscale features, CD spectroscopy normally requires wavelength-swept laser sources as well as wavelength-specific optical accessories. Here, we experimentally demonstrate an orbital-angular-momentum-assisted approach to yield chiroptical signals with monochromatic light. The gigantic vortical differential scattering (VDS) of ∼120% is achieved on intrinsically chiral microstructures fabricated by femtosecond laser. The VDS measurements can robustly generate chiroptical properties on microstructures with varying geometric features (e.g., diameters and helical pitches) and detect chiral molecules with high sensitivity. This VDS scheme lays a paradigm-shift pavement toward efficiently chiroptical discrimination of multiscale chiral structures with photonic orbital angular momentum. It simplifies and complements the conventional CD spectroscopy, opening possibilities for measuring weak optical chirality, especially on mesoscale chiral architectures and macromolecules.”

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Publication: Proceedings of the National Academy of Sciences
Issue/Year: Proceedings of the National Academy of Sciences, Volume 118; Number 2; Pages e2020055118; 2020
DOI: 10.1073/pnas.2020055118

Zeroth- and first-order long range non-diffracting GausstextendashBessel beams generated by annihilating multiple-charged optical vortices

Author(s):

Stoyanov, Lyubomir; Zhekova, Maya; Stefanov, Aleksander; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“We demonstrate an alternative approach for generating zeroth- and first-order long range non-diffracting Gauss–Bessel beams (GBBs). Starting from a Gaussian beam, the key point is the creation of a bright ring-shaped beam with a large radius-to-width ratio, which is subsequently Fourier-transformed by a thin lens. The phase profile required for creating zeroth-order GBBs is flat and helical for first-order GBBs with unit topological charge (TC). Both the ring-shaped beam and the required phase profile can be realized by creating highly charged optical vortices by a spatial light modulator and annihilating them by using a second modulator of the same type. The generated long-range GBBs are proven to have negligible transverse evolution up to 2 m and can be regarded as non-diffracting. The influences of the charge state of the TCs, the propagation distance behind the focusing lens, and the GBB profiles on the relative intensities of the peak/rings are discussed. The method is much more efficient as compared to this using annular slits in the back focal plane of lenses. Moreover, at large propagation distances the quality of the generated GBBs significantly surpasses this of GBBs created by low angle axicons. The developed analytical model reproduces the experimental data. The presented method is flexible, easily realizable by using a spatial light modulator, does not require any special optical elements and, thus, is accessible in many laboratories.”

Link to Publications Page

Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-78613-7

Laser photonic-reduction stamping for graphene-based micro-supercapacitors ultrafast fabrication

Author(s):

Yuan, Yongjiu; Jiang, Lan; Li, Xin; Zuo, Pei; Xu, Chenyang; Tian, Mengyao; Zhang, Xueqiang; Wang, Sumei; Lu, Bing; Shao, Changxiang; Zhao, Bingquan; Zhang, Jiatao; Qu, Liangti & Cui, Tianhong

Abstract:

“Micro-supercapacitors are promising miniaturized energy storage devices that have attracted considerable research interest. However, their widespread use is limited by inefficient microfabrication technologies and their low energy density. Here, a flexible, designable micro-supercapacitor can be fabricated by a single pulse laser photonic-reduction stamping. A thousand spatially shaped laser pulses can be generated in one second, and over 30,000 micro-supercapacitors are produced within 10 minutes. The micro-supercapacitor and narrow gaps were dozens of microns and 500 nm, respectively. With the unique three-dimensional structure of laser-induced graphene based electrode, a single micro-supercapacitor exhibits an ultra-high energy density (0.23 Wh cm−3), an ultra-small time constant (0.01 ms), outstanding specific capacitance (128 mF cm−2 and 426.7 F cm−3) and a long-term cyclability. The unique technique is desirable for a broad range of applications, which surmounts current limitations of high-throughput fabrication and low energy density of micro-supercapacitors.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 11; Number 1; 2020
DOI: 10.1038/s41467-020-19985-2

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: 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: 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: 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: Vol. 2, Issues 2 (2020)
DOI: 10.1117/1.AP.2.2.026001