Singular skeleton evolution and topological reactions in edge-diffracted circular optical-vortex beams

Bekshaev, A. Ya.; Chernykh, Aleksey V.; Khoroshun, Anna; Mikhaylovskaya, Lidiya

doi:10.1016/j.optcom.2017.03.062

Cited by 25 publications

(58 citation statements)

References 29 publications

(150 reference statements)

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“…However, it does not hold for the Fresnel DPs determined by Eq. ( 2): in agreement with other similar situations [16][17][18][19][20][21][22], examples of Fig. 1b calculated by Eq.…”

supporting

confidence: 90%

“…To the best of our knowledge, the most flexible and universal approaches exploit specific features of the OV diffraction in which the helical properties of an OV and its OAM-related circulatory nature are explicitly manifested. The simplest edge diffraction schemes [16][17][18] provide spectacular demonstration of the transverse energy circulation but a reliable detection of the OV "strength" (TC magnitude |m|) requires additional timeconsuming and precise procedures. More efficient methods enabling the "full" (TC magnitude + sign) OV diagnostics are based on the traditional approaches employing a single or double slit [19,20] and strip [21,22] Fresnel diffraction.…”

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confidence: 99%

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Optical-vortex diagnostics via Fraunhofer slit diffraction with controllable wavefront curvature

et al. 2020

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Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX Far-field slit-diffraction of circular optical-vortex (OV) beams is efficient for measurement of the topological charge (TC) magnitude but does not reveal its sign. We show that this is because in the common diffraction schemes the diffraction plane coincides with the incident OV waist plane. With explicit involvement of the incident beam spherical wavefront and based on the examples ofLaguerre-Gaussian modes we show that the far-field profile possesses an asymmetry depending on the wavefront curvature and the TC sign. These features enable simple and efficient ways for the simultaneous diagnostics of the TC magnitude and sign, which can be useful in many OV applications, including the OV-assisted metrology and information processing.

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“…However, it does not hold for the Fresnel DPs determined by Eq. ( 2): in agreement with other similar situations [16][17][18][19][20][21][22], examples of Fig. 1b calculated by Eq.…”

supporting

confidence: 90%

mentioning

confidence: 99%

Optical-vortex diagnostics via Fraunhofer slit diffraction with controllable wavefront curvature

et al. 2020

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“…Its main difference from the simulation results is that it does not show the rotation accelerations near  r = /2, 3/2 where one of the OVs crosses the negative y half-axis. These accelerations correspond to the trajectories' "jumps" observed in the diffracted Kummer OV beams and can be explained within the frame of the improved analytical model for the OV beam diffraction [32,33,36]. In the whole, the far-field pattern of the diffracted OV beam supplies an interesting example where the input wavefront curvature is transformed into the output azimuthal rotation of the secondary OV pair, which can possibly find applications for the wavefront diagnostics and measurements.…”

Section: 1mentioning

confidence: 74%

Displacements and evolution of optical vortices in edge-diffracted Laguerre–Gaussian beams

Bekshaev

Chernykh

Khoroshun

et al. 2017

J. Opt.

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Based on the Kirchhoff-Fresnel approximation, we consider behavior of the optical vortices (OV) upon propagation of the diffracted Laguerre-Gaussian (LG) beams with topological charge |m| = 1, 2. Under conditions of weak diffraction perturbation (i.e. the diffraction obstacle covers only the far transverse periphery of the incident LG beam), the OVs describe almost perfect 3D spirals within the diffracted beam body, which is an impressive demonstration of the helical nature of an OV beam. The far-field OV positions within the diffracted beam cross section depend on the wavefront curvature of the incident OV beam so that the input wavefront curvature is transformed into the output azimuthal OV rotation. The results can be useful in the OV metrology and for the OV beam's diagnostics. IntroductionDuring the past decades, light beams with optical vortices (OV) attract close attention of the optical community [1][2][3][4]. These intriguing optical objects, closely associated with the topological phase singularities, spectacularly illustrate the deep and fruitful optical-mechanical analogies and universality of physical laws [1-6] as well as provide a lot of inspiring applications in precise metrology [7][8][9][10][11][12][13][14], information transfer and processing [15][16][17] and micromanipulation techniques [18][19][20]. In particular, the edge diffraction of OVs has been studied intensively [21][22][23][24][25][26][27][28][29][30][31][32][33] enabling visual manifestation of the unique OV properties associated with their helical nature. One of the most impressive evidences of the helical energy flow in OV beams is the recently revealed spirallike motion of the OV cores (amplitude zeros) within the diffracted beam cross section, that occurs when the screen edge performs a monotonous translation in the transverse direction towards or away from the beam axis [31][32][33].The similar rotational motion of the OV cores is expected when the screen edge rests but the longitudinal evolution of the propagating diffracted beam is observed behind the screen. Under such conditions, the evolution of phase singularities in propagating edge-diffracted beams was studied in many details [28][29][30]. In these works, the main attention was paid to severely screened OV beams, in which the diffracted beam structure is strongly perturbed by the obstacle, and its evolution is accompanied by multiple topological events: the OV disappearance and regeneration, emergence of new OVs, their interactions and topological reactions, etc. This performance is interesting and valuable for diverse metrological purposes but the presence of additional factors mask the expected

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“…As a generic example of the input OV beam, we consider a Laguerre-Gaussian mode LG pm with zero radial index p [2][3][4]. This is a usual simplification rather typical for the studies of the OV beams' transformations [23][24][25][26][27][28][29][30][31]34,36]. But if the incident LG beam is multicharged (|m| > 1), the multiple "secondary" OVs separately evolve in the diffracted beam.…”

Section: Introductionmentioning

confidence: 99%

Transformation of the singular skeleton in optical-vortex beams diffracted by a rectilinear phase step

Bekshaev

Khoroshun

Mikhaylovskaya

2019

J. Opt.

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Based on the Kirchhoff-Fresnel approximation, we numerically analyze spatial characteristics of the light field formed after a circular Laguerre-Gaussian beam with a single-charged optical vortex (OV) passes the transparent screen with a rectilinear phase step. The main attention is paid to the localization and interactions of the OVs, which form the singular skeleton of the transformed field. The phase-step influence depends on its value and position with respect to the beam axis. Upon "weak perturbation" (low phase step) the main effect is that the OV is shifted from the initial axial position and describes a closed loop when the phase step is monotonously translated across the beam. The "strong perturbation" (the phase step is close to ) induces topological reactions with emergence and annihilation of additional singularities in the near-axial region of the diffracted beam cross section. These features are interpreted based on the 3D OV trajectories that show an intricate behavior with kinks and "retrograde" segments. The details of the OV migration and singular skeleton transformations reveal the fundamental helical nature and transverse energy circulation in the OV beams. The numerical results obtained in this paper show possibilities for the purposeful control of the singular skeleton characteristics within the transformed beam, and can be useful for the OV diagnostics, OV metrology and micromanipulation techniques.

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Singular skeleton evolution and topological reactions in edge-diffracted circular optical-vortex beams

Cited by 25 publications

References 29 publications

Optical-vortex diagnostics via Fraunhofer slit diffraction with controllable wavefront curvature

Optical-vortex diagnostics via Fraunhofer slit diffraction with controllable wavefront curvature

Displacements and evolution of optical vortices in edge-diffracted Laguerre–Gaussian beams

Transformation of the singular skeleton in optical-vortex beams diffracted by a rectilinear phase step

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