High-Flexibility Control of Structured Light with Combined Adaptive Optical Systems

Author(s):

Grunwald, Rüdiger; Jurke, Mathias; Bock, Martin; Liebmann, Max; Bruno, Binal Poyyathuruthy; Gowda, Hitesh & Wallrabe, Ulrike

Abstract:

“Combining the specific advantages of high-resolution liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs) and reflective or refractive micro-electro-mechanical systems (MEMS) presents new prospects for the generation of structured light fields. In particular, adaptive self-apodization schemes can significantly reduce diffraction by low-loss spatial filtering. The concept enables one to realize low-dispersion shaping of nondiffracting femtosecond wavepackets and to temporally switch, modulate or deflect spatially structured beams. Adaptive diffraction management by structured illumination is demonstrated for piezo-based and thermally actuated axicons, spiral phase plates (SPPs) and Fresnel bi-mirrors. Improved non-collinear autocorrelation with angular-tunable Fresnel-bi-mirrors via self-apodized illumination and phase contrast of an SLM is proposed. An extension of the recently introduced nondiffractive Talbot effect to a tunable configuration by combining an SLM and a fluid lens is reported. Experimental results for hexagonal as well as orthogonal array beams are presented.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 42; 2022
DOI: 10.3390/photonics9010042

Electro-Optic Modulation of Higher-Order Poincar’e Beam Based on Nonlinear Optical Crystal

Author(s):

Han, Lu; Li, Zhan; Chen, Chao; Sun, Xin; Zhang, Junyong & Liu, Dean

Abstract:

“Vector beams (VBs) have spatially inhomogeneous polarization states distribution and have been widely used in many fields. In this paper, we proposed a method to modulate polarization states of higher-order Poincaré (HOP) beams and designed a system based on Mach-Zehnder interferometers, in which polarization state (include azimuth and ellipticity) of generated HOP beams were modulated by linear electro-optic (EO) effect of nonlinear optical crystals. Using this method, the polarization state of generated HOP beams could be controlled by voltage signal applied on EO crystals, which makes the process of the polarization state change with no optical element moving and mechanical vibrations. Besides, due to the flexibility of the voltage signal, the polarization state could be switched directly and immediately.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 41; 2022
DOI: 10.3390/photonics9010041

Focal beam structuring by triple mixing of optical vortex lattices

Author(s):

Stoyanov, Lyubomir; Maleshkov, Georgi; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“On-demand generation and reshaping of arrays of focused laser beams is highly desired in many areas of science and technology. In this work, we present a versatile approach for laser beam structuring in the focal plane of a lens by triple mixing of square and/or hexagonal optical vortex lattices (OVLs). In the artificial far field the input Gaussian beam is reshaped into ordered arrays of bright beams with flat phase profiles. This is remarkable, since the bright focal peaks are surrounded by hundreds of OVs with their dark cores and two-dimensional phase dislocations. Numerical simulations and experimental evidences for this are shown, including a broad discussion of some of the possible scenarios for such mixing: triple mixing of square-shaped OVLs, triple mixing of hexagonal OVLs, as well as the two combined cases of mixing square-hexagonal-hexagonal and square-square-hexagonal OVLs. The particular ordering of the input phase distributions of the OV lattices on the used spatial light modulators is found to affect the orientation of the structures ruled by the hexagonal OVL. Reliable control parameters for the creation of the desired focal beam structures are the respective lattice node spacings. The presented approach is flexible, easily realizable by using a single spatial light modulator, and thus accessible in many laboratories.”

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Publication: Optical and Quantum Electronics
Issue/Year: Optical and Quantum Electronics, Volume 54; Number 1; 2021
DOI: 10.1007/s11082-021-03399-5

Generating a twisted Gaussian Schell-model beam with a coherent-mode superposition

Author(s):

Zhang, Yue; Zhang, Xuan; Wang, Haiyun; Ye, Yan; Liu, Lin; Chen, Yahong; Wang, Fei & Cai, Yangjian

Abstract:

“Twist phase is a nontrivial second-order phase that only exists in a partially coherent field, providing a new degree of freedom for manipulating statistical properties of random light. However, in the existing experimental methods either it is difficult to control the twist phase or requires a large number of pseudo/random modes to approximately synthesize the twisted beams. In this work, we demonstrate a simple and efficient approach, based on the superposition of mutually orthogonal Laguerre-Gaussian modes with appropriate mode weights, to generate the twisted beams with a controllable twist phase. We show that a smaller number of modes are required to synthesize the twisted beams, compared to the pseudo-mode superposition, because the orthogonal coherent modes are used in the present method. We experimentally generate the twisted Gaussian Schell-model beams with controllable strength of twist phase and measure their degree of coherence and average intensity behavior during propagation. The experimental results agree well with the theoretical predictions. Our approach will promote the application of the twisted partially coherent beams in optical imaging and free-space optical communications.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 25; Pages 41964; 2021
DOI: 10.1364/oe.446160

Realization and measurement of Airy transform of Gaussian vortex beams

Author(s):

Zhou, Lu; Zhou, Tong; Wang, Fei; Li, Xia; Chen, Ruipin; Zhou, Yimin & Zhou, Guoquan

Abstract:

“Airy transformation is a useful technique to modulate amplitude and phase of a light beam, which has important applications in particle trapping/manipulation, optical communications and optical imaging. However, most of the studies only focused on the Airy transform of Gaussian beams and other vortex-free beams in the past. In this paper, the Airy transform of Gaussian vortex beams, which are the most common vortex beams, is investigated. A universal analytical expression of the Gaussian vortex beams with topological charge (TC) m passing through an Airy transform optical system is derived. We carry out a detailed study on the output beams’ characteristics after the Airy transform of the Gaussian vortex beams with m = ± 1 and ± 2. The analytical expressions for the centroid, the beam spot size, the divergence angle and the beam propagation factor of the output beams are derived. The effects of the Airy control parameters and the TC on the normalized intensity distribution, the phase distribution, the centroid, the beam spot size and the beam propagation factor of the output beams are investigated both theoretically and experimentally. The experimental results agree reasonably well with the theoretical results which illustrate the properties of Airy transform of the Gaussian vortex beams.”

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Publication: Optics and Laser Technology
Issue/Year: Optics and Laser Technology, Volume 143; Pages 107334; 2021
DOI: 10.1016/j.optlastec.2021.107334

Caustic Interpretation of the Abruptly Autofocusing Vortex beams

Author(s):

Xiao, Na; Xie, Chen; Jia, Erse; Li, Jiaying; Giust, Remo; Courvoisier, François & Hu, Minglie

Abstract:

“We propose an effective scheme to interpret the abruptly autofocusing vortex beam. In our scheme, a set of analytical formulae are deduced to well predict not only the global caustic, before and after the focal plane, but also the focusing properties of the abruptly autofocusing vortex beam, including the axial position as well as the diameter of focal ring. Our analytical results are in excellent agreement with both numerical simulation and experimental results. Besides, we apply our analytical technique to the fine manipulation of the focusing properties with a scaling factor. This set of methods would be beneficial to a broad range of applications such as particle trapping and micromachinings.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 13; Pages 19975; 2021
DOI: 10.1364/oe.430497

Controllable axial optical chain beams using a holographic method

Author(s):

Song, Xianlin; Wei, Jianshuang; Teng, Ao & Zhao, Aojie

Abstract:

“Axial optical chain (optical bottle beams) beams are widely used in optical micromanipulation, atom trapping, guiding and binding of microparticles and biological cells, etc. However, the generation of axial optical chain beams are not very flexible at present, and its important characteristics such as periodicity and phase shift cannot be easily regulated. Here, we propose a holographic method to achieve the axial optical chain beams with controllable periodicity and phase. A double annular phase diagram is generated based on the gratings and lenses algorithms. The beam incident to the double annular slits was tilted from the optical axis to produce concentric double annular beams. The annular beam with different radius will produce the zero-order Bessel beam with different axial wave vector. Axial optical chain beams is produced by interference of two zero-order Bessel beams with different axial wave vectors. The phase and periodicity of the axial optical chain beams can be changed by changing the initial phase difference and radius of the double annular slits of the double annular phase diagram, respectively. The feasibility and effectiveness of the proposed method are demonstrated by theoretical numerical analysis and experiments. This method will further expand the application of axial optical chain beams in optical tweezers, optical modulation and other fields.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 11; Pages 17304; 2021
DOI: 10.1364/oe.421852

Generation of Complex Transverse Energy Flow Distributions with Autofocusing Optical Vortex Beams

Author(s):

Khonina, Svetlana N.; Porfirev, Alexey P.; Ustinov, Andrey V. & Butt, Muhammad Ali

Abstract:

“Optical vortex (OV) beams are widely used for the generation of light fields with transverse energy flow inducing orbital motion of the nano- and microparticles in the transverse plane. Here, we present some new modifications of OV beams with autofocusing properties for shaping complex transverse energy flow distributions varying in space. The angular component of the complex amplitude of these beams is defined by the superpositions of OV beams with different topological charges. The proposed approach provides a convenient method to control the three-dimensional structure of the generated autofocusing OV beams. The control of the transverse distribution of an autofocusing beam provides a wide variety of generated fields with both rotating and periodic properties, which can be used in the field of laser manipulation and laser material processing. Thus, the obtained numerical results predict different types of motion of the trapped particles for the designed OV autofocusing beams. The experimental results agree with modeling results and demonstrate the principal possibility to shape such laser beams using spatial light modulators.”

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Publication: Micromachines
Issue/Year: Micromachines, Volume 12; Number 3; Pages 297; 2021
DOI: 10.3390/mi12030297

Laser beam shaping based on amplitude-phase control of a fiber laser array

Author(s):

Adamov, E. V.; Aksenov, V. P.; Atuchin, V. V.; Dudorov, V. V.; Kolosov, V. V. & Levitsky, M. E.

Abstract:

“A new technique is suggested for the generation of laser beams with an intensity profile specified. The technique is based on the coherent combining of radiation of a fiber laser array with adaptive control of the power and phase of Gaussian subbeams with plane wavefronts. The power and phase of the subbeams are determined for each intensity profile specified in the far field based on the inverse problem solution, for example, by the Gershberg–Saxton method. To form a required phase profile, the stochastic parallel gradient descent (SPGD) method is used along with the inversion of a required phase distribution with a phase corrector. The main advantages of the technique are the adaptive control of the intensity profile and a possibility of generating high-power laser beams. The results of numerical and field experiments are described.”

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Publication: OSA Continuum
Issue/Year: OSA Continuum, Volume 4; Number 1; Pages 182; 2021
DOI: 10.1364/osac.413956

Deep-learning-based high-resolution recognition of fractional-spatial-mode-encoded data for free-space optical communications

Author(s):

Na, Youngbin & Ko, Do-Kyeong

Abstract:

“Structured light with spatial degrees of freedom (DoF) is considered a potential solution to address the unprecedented demand for data traffic, but there is a limit to effectively improving the communication capacity by its integer quantization. We propose a data transmission system using fractional mode encoding and deep-learning decoding. Spatial modes of Bessel-Gaussian beams separated by fractional intervals are employed to represent 8-bit symbols. Data encoded by switching phase holograms is efficiently decoded by a deep-learning classifier that only requires the intensity profile of transmitted modes. Our results show that the trained model can simultaneously recognize two independent DoF without any mode sorter and precisely detect small differences between fractional modes. Moreover, the proposed scheme successfully achieves image transmission despite its densely packed mode space. This research will present a new approach to realizing higher data rates for advanced optical communication systems.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 11; Number 1; 2021
DOI: 10.1038/s41598-021-82239-8
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