Direct comparison of anti-diffracting optical pin beams and abruptly autofocusing beams

Author(s):

Denghui Li, Domenico Bongiovanni, Michael Goutsoulas, Shiqi Xia, Ze Zhang, Yi Hu, Daohong Song, Roberto Morandotti, Nikolaos K. Efremidis, and Zhigang Chen

Abstract:

“We propose and demonstrate a generalized class of anti-diffracting optical pin-like beams (OPBs). Such beams exhibit autofocusing dynamics while morphing into a Bessel-like shape during long-distance propagation, where the size of their main lobe can be tuned by an exponent’s parameter. In particular, their amplitude envelope can be engineered to preserve the pin-like peak intensity pattern. In both theory and experiment, the OPBs are directly compared with radially symmetric abruptly autofocusing beams (AABs) under the same conditions. Furthermore, enhanced transmission and robustness of the OPBs are observed while traversing a scattering colloidal suspension, as compared to both AABs and conventional Bessel beams.”

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Publication: OSA Continuum
Issue/Year/DOI: Vol. 3, Issue 6, pp. 1525-1535 (2020)
DOI: 10.1364/OSAC.391878

Hologram generation via Hilbert transform

Author(s):

Tomoyoshi Shimobaba, Takashi Kakue, Yota Yamamoto, Ikuo Hoshi, Harutaka Shiomi, Takashi Nishitsuji, Naoki Takada, and Tomoyoshi Ito

Abstract:

“We propose an indirect method for generating a complex hologram and phase-only hologram from an amplitude hologram using the Hilbert transform. The Hilbert transform generates an imaginary part of complex amplitude from only an amplitude hologram, resulting in the reduction of the total computational complexity of complex and phase-only holograms. More importantly, the proposed method can reduce the hardware resources of dedicated hologram processors.”

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Publication: OSA Continuum
Issue/Year/DOI: Vol. 3, Issue 6, pp. 1498-1503 (2020)
DOI: 10.1364/OSAC.395003

Deep neural networks in single-shot ptychography

Author(s):

Omri Wengrowicz, Or Peleg, Tom Zahavy, Barry Loevsky, and Oren Cohen

Abstract:

“We develop and explore a deep learning based single-shot ptychography reconstruction method. We show that a deep neural network, trained using only experimental data and without any model of the system, leads to reconstructions of natural real-valued images with higher spatial resolution and better resistance to systematic noise than common iterative algorithms.”

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Publication: Optics Express
Issue/Year/DOI: Vol. 28, Issue 12, pp. 17511-17520
DOI: 10.1364/OE.393961

Rotational Doppler shift upon reflection from a right angle prism

Author(s):

O. Emile, J. Emile and C. Brousseau

Abstract:

“This Letter reports the observation of a rotational Doppler shift on reflected beams carrying Orbital Angular Momentum (OAM). More precisely, we study the beat frequency of two optical beams carrying OAM with opposite signs, reflected on a right angle prism. We show that the interference of the two beams leads to a daisy-like pattern that rotates at twice the rotating frequency of the prism. The rotational Doppler frequency shift is equal to the OAM topological charge change times the rotational frequency. Possible applications in the positioning and detection of rotation of objects are then discussed.
This publication was supported by the European Union through the European Research Development Fund (ERDF) and the French Region of Brittany, Ministry of High Education and Research, Rennes Métropole and Conseil Départemental 35, through The CPER project SOPHIE/STIC and Ondes. We wish to acknowledge valuable discussions with Professor K. Mahdjoubi (Université de Rennes 1).”

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Publication: Applied Physics Letters

Issue/Year/DOI: Appl. Phys. Lett. Volume:116 (2020)
DOI: 10.1063/5.0009396

Non-interferometric technique to realize vector beams embedded with polarization singularities

Author(s):

Praveen Kumar, Sushanta Kumar Pal, Naveen K. Nishchal, and P. Senthilkumaran

Abstract:

“In this paper, we present a simple and flexible non-interferometric method to generate various polarization singularity lattice fields. The proposed method is based on a double modulation technique that uses a single reflective spatial light modulator to generate different lattice structures consisting of V-point and C-point polarization singularities. The present technique is compact with respect to previous experimental realization techniques. Different structures having star and lemon fields are generated without altering the experimental setup. In addition, the same setup can be used to obtain different types of inhomogeneous fields embedded with isolated polarization singularities even of higher orders. The Stokes polarimetry method has been used to obtain the polarization distributions of generated fields, which are in good agreement with simulated results.”

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Publication: Journal of the Optical Society of America A
Issue/Year/DOI: Vol. 37, Issue 6, pp. 1043-1052 (2020)
DOI: 10.1364/JOSAA.393027

Optical vortex with multi-fractional orders

Author(s):

Juntao Hu, Yuping Tai, Liuhao Zhu, Zixu Long, Miaomiao Tang, Hehe Li, Xinzhong Li and Yangjian Cai

Abstract:

“Recently, optical vortices (OVs) have attracted substantial attention because they can provide an additional degree of freedom, i.e., orbital angular momentum (OAM). It is well known that the fractional OV (FOV) is interpreted as a weighted superposition of a series of integer OVs containing different OAM states. However, methods for controlling the sampling interval of the OAM state decomposition and determining the selected sampling OAM state are lacking. To address this issue, in this Letter, we propose a FOV by inserting multiple fractional phase jumps into whole phase jumps (2π), termed as a multi-fractional OV (MFOV). The MFOV is a generalized FOV possessing three adjustable parameters, including the number of azimuthal phase periods (APPs), N; the number of whole phase jumps in an APP, K; and the fractional phase jump, α. The results show that the intensity and OAM of the MFOV are shaped into different polygons based on the APP number. Through OAM state decomposition and OAM entropy techniques, we find that the MFOV is constructed by sparse sampling of the OAM states, with the sampling interval equal to N. Moreover, the probability of each sampling state is determined by the parameter α, and the state order of the maximal probability is controlled by the parameter K, as K * N. This work presents a clear physical interpretation of the FOV, which deepens our understanding of the FOV and facilitates potential applications, especially for multiplexing technology in optical communication based on OAM.
This work was supported by the National Natural Science Foundation of China (NSFC) (Nos. 11974102, 11525418, 91750201, and 11974218), the Open Research Fund of State Key Laboratory of Transient Optics and Photonics, CAS (No. SKLST201901), the Innovation Group of Jinan under Grant No. 2018GXRC010, and the National key Research and Development Project of China (2019YFA0705000).”

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Publication: Applied Physics Letters
Issue/Year/DOI: Appl. Phys. Lett. Volume:116 (2020)
DOI: 10.1063/5.0004692

Flexible measurement of high-order optical orbital angular momentum with a variable cylindrical lens pair

Author(s):

Jianneng Lu, Chongyang Cao, Zhuqing Zhu and Bing Gu

Abstract:

“We present a method to measure the high-order optical orbital angular momentum (OAM) with a variable cylindrical lens pair. The optical system consists of two cylindrical lenses with the opposite focal length. It produces a rotating position—spatial frequency transformation of phase modulation by changing the angle between the two cylindrical lenses. With this feature, the method can flexibly measure the OAM states of the vortex beams with different beam waists. The OAM states are determined by the number and direction of dark stripes of the diffraction pattern. The measurements of the topological charge and the radial index of Laguerre–Gaussian mode are demonstrated. As a compact high-order OAM measuring device, the variable cylindrical lens pair may find potential applications in optical communication.
This work was funded by the National Natural Science Foundation of China (Nos. 11774055 and 61875093), the Natural Science Foundation of Jiangsu Province of China (No. BK20181384) and the Natural Science Foundation of Tianjin of China (No. 19JCYBJC16500).”

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Publication: Applied Physics Letters

Issue/Year/DOI: Appl. Phys. Lett. Volume:116 (2020)
DOI: 10.1063/5.0002756

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

High-resolution imaging system with an annular aperture of coded phase masks for endoscopic applications

Author(s):

Nitin Dubey, Joseph Rosen, and Israel Gannot

Abstract:

“Partial aperture imaging is a combination of two different techniques; coded aperture imaging and imaging through an aperture that is only a part of the complete disk, commonly used as the aperture of most imaging systems. In the present study, the partial aperture is a ring where the imaging through this aperture resolves small details of the observed scene similarly to the full disk aperture with the same diameter. However, unlike the full aperture, the annular aperture enables using the inner area of the ring for other applications. In this study, we consider the implementation of this special aperture in medical imaging instruments, such as endoscopes, for imaging internal cavities in general and of the human body in particular. By using this annular aperture, it is possible to transfer through the internal open circle of the ring other elements such as surgical tools, fibers and illumination devices. In the proposed configuration, light originated from a source point passes through an annular coded aperture and creates a sparse, randomly distributed, intensity dot pattern on the camera plane. A combination of the dot patterns, each one recorded only once, is used as the point spread hologram of the imaging system. The image is reconstructed digitally by cross correlation between the object intensity response and the point spread hologram.”

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Publication: Optics Express

Issue/Year/DOI: Vol. 28, Issue 10, pp. 15122-15137
DOI: 10.1364/OE.391713

Fabrication of oil–water separation copper filter by spatial light modulated femtosecond laser

Author(s):

Xiaoyan Sun, Zhuolin Dong, Kaifan Cheng, Dongkai Chu, Dejian Kong, Youwang Hu and Ji’an Duan

Abstract:

“Surface with oil–water separation performance has attracted more and more attention in the application of oil-containing wastewater purification. Much related work has been done by many researchers. However, there are still many difficulties in rapid manufacturing of filter membranes with special wettability. In this paper, an efficient, flexible method to fabricate microporous arrays by using a femtosecond (fs) laser combined with a spatial light modulator is proposed. The laser treated copper sheet surface shows hydrophobic and superoleophilic properties due to the microstructure. Meanwhile, the array of micro-through-holes on the surface can allow oil to penetrate through holes and prevent water from penetrating. The manufacturing process is not only extremely efficient, with a 10 × 10 focus array used in the ablation, but also it is without chemical method and the filter presents a long-term stable hydrophobic and superoleophilic performance.”

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Publication: Journal of Micromechanics and Microengineering

Issue/Year/DOI: Volume 30, Number 6
DOI: 10.1088/1361-6439/ab870d

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