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

WISHED: Wavefront imaging sensor with high resolution and depth ranging

Author(s):

Yicheng Wu, Fengqiang Li, Florian Willomitzer, Ashok Veeraraghavan, Oliver Cossairt

Abstract:

“Phase-retrieval based wavefront sensors have been shown to reconstruct the complex field from an object with a high spatial resolution. Although the reconstructed complex field encodes the depth information of the object, it is impractical to be used as a depth sensor for macroscopic objects, since the unambiguous depth imaging range is limited by the optical wavelength. To improve the depth range of imaging and handle depth discontinuities, we propose a novel three-dimensional sensor by leveraging wavelength diversity and wavefront sensing. Complex fields at two optical wavelengths are recorded, and a synthetic wavelength can be generated by correlating those wavefronts. The proposed system achieves high lateral and depth resolutions. Our experimental prototype shows an unambiguous range of more than 1,000 x larger compared with the optical wavelengths, while the depth precision is up to 9µm for smooth objects and up to 69µm for rough objects. We experimentally demonstrate 3D reconstructions for transparent, translucent, and opaque objects with smooth and rough surfaces.”

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Publication: 2020 IEEE International Conference on Computational Photography (ICCP)
DOI: 10.1109/ICCP48838.2020.9105280

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

Method for single-shot fabrication of chiral woodpile photonic structures using phase-controlled interference lithography

Author(s):

Swagato Sarkar, Krishnendu Samanta, and Joby Joseph

Abstract:

“In this report, we propose a large-area, scalable and reconfigurable single-shot
optical fabrication method using phase-controlled interference lithography (PCIL) to realize
submicrometer chiral woodpile photonic structures. This proposed technique involves a 3 + 3
double-cone geometry with beams originated from a computed phase mask displayed on a single
spatial light modulator. Simulation studies show the filtering response of such structures for
linearly polarized plane wave illumination, with structural features tunable through a single
parameter of interference angle. Further, these single chiral woodpile structures show dual
chirality on illumination with both right circularly and left circularly polarized light through
simulation. Experimentally fabricated patterns on photoresist show resemblance to the desired
chiral woodpile structures.”

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Publication: Optics Express

Issue/Year/DOI: Volume 28, Issue 3, pp. 4347-4361
DOI: 10.1364/OE.384987

Rapid phase calibration of a spatial light modulator using novel phase masks and optimization of its efficiency using an iterative algorithm

Author(s):

Amar Deo Chandra and Ayan Banerjee

Abstract:

“We develop an improved phase calibration method of a reflective SLM using interferometry by employing novel phase masks. In the process, we definitively determine the actual maximum phase throw of our SLM which provides a recipe for users to verify supplier specifications. We generate optimised phase masks by using Iterative Fourier Transform Algorithm (IFTA) and compare their performance with global linear corrections in the look-up table (LUT) and find that the former perform with around 20% better efficiency. Besides obtaining an array of 1D/2D spots having high uniformity (90%) using IFTA, our result exemplifies the use of iterative algorithms for improving efficiency of phase limited SLMs. Finally, our improved phase calibration method enables threefold faster phase measurements, and to the best of our knowledge, is the first endeavour directed towards enabling rapid phase characterisation of an SLM using interferometric measurements. We believe that it can have very useful applications in settings which may require fast phase calibrations as well as for real-time, multi-wavelength spectroscopic applications.”

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Publication: Journal of Modern Optics

Issue/Year/DOI: Volume 67- Issue 7
DOI: 10.1080/09500340.2020.1760954

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

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