Spatiotemporal Optical Vortices

Jhajj, N.; Larkin, Ilia; Rosenthal, Eric; Zahedpour, S.; Wahlstrand, J. K.; Milchberg, H. M.

doi:10.1103/physrevx.6.031037

Cited by 150 publications

(112 citation statements)

References 38 publications

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“…tructured light has recently gained increased interest in that it can accommodate the production of uniquely propagating beams of light [1][2][3][4][5] . One particularly interesting aspect is the ability of a structured beam to carry orbital angular momentum (OAM) [6][7][8][9][10][11] . One form of momentum is a simple Gaussian beam dot that can rotate in a circular fashion as it propagates, illuminating a ring shape [12][13][14] ; this OAM is similar to revolution around a central axis.…”

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confidence: 99%

Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

et al. 2020

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Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest. In terms of changes in time, OAM can be manifest at a given distance in different forms, including: (1) a Gaussian-like beam dot that revolves around a central axis, and (2) a Laguerre-Gaussian (LG ';p) beam with a helical phasefront rotating around its own beam center. Here we explore the generation of dynamic spatiotemporal beams that combine these two forms of orbital-angular-momenta by coherently adding multiple frequency comb lines. Each line carries a superposition of multiple LG ';p modes such that each line is composed of a different ' value and multiple p values. We simulate the generated beams and find that the following can be achieved: (a) mode purity up to 99%, and (b) control of the helical phasefront from 2π-6π and the revolving speed from 0.2-0.6 THz. This approach might be useful for generating spatiotemporal beams with even more sophisticated dynamic properties.

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confidence: 99%

Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

et al. 2020

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“…This interaction is attractive if the filaments are in phase, and repulsive if they are in antiphase [27,28], corresponding to constructive and destructive interferences in the photon bath, respectively. Previous theoretical and experimental studies have shown that the relative phase between filaments is mainly randomly driven by intensity fluctuations during the collapse [29] and is then stabilized for the filaments propagating after the collapse [30].Recently we showed that at laser powers exceeding 100 TW, this mutual interaction limits the density of filaments in the transverse beam profile [31], resulting in the * corresponding author jean-pierre.wolf@unige.ch rise of the photon bath intensity. As a consequence, the photon bath effectively contributes to non-linear effects like white-light generation [32] or laser-induced condensation [33], resulting in an overall increase of the yield of these processes.…”

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Gas-Solid Phase Transition in Laser Multiple Filamentation

et al. 2017

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While propagating in transparent media, near-infrared multi-terawatt (TW) laser beams break up in a multitude of filaments of typically 100-200 um diameter with peak intensities as high as 10 to 100 TW/cm 2 . We observe a phase transition at incident beam intensities of 0.4 TW/cm 2 , where the interaction between filaments induce solid-like 2-dimensional crystals with a 2.7 mm lattice constant, independent of the initial beam diameter. Below 0.4 TW/cm 2 , we evidence a mixed phase state in which some filaments are closely packed in localized clusters, nucleated on inhomogeneities (seeds) in the transverse intensity profile of the beam, and other are sparse with almost no interaction with their neighbors, similar to a gas. This analogy with a thermodynamic gas-solid phase transition is confirmed by calculating the interaction Hamiltonian between neighboring filaments, which takes into account the effect of diffraction, Kerr self-focusing and plasma generation. The shape of the effective potential is close to a Morse potential with an equilibrium bond length close to the observed value.Many physical systems are well described by statistical models driven by nearest-neighbor interactions, such as spin models [1][2][3]. Recently, we showed that the formation of multiple filamentation patterns in high-power ultrashort laser pulses also belong to this category [4,5].Laser filaments are produced in high-power, ultrashort laser pulses propagating in air or other transparent media [6][7][8] by a dynamic balance between Kerr selffocusing, and defocusing by higher-order non-linear effects including the ionization of the medium and other polarization saturation terms [9,10]. At 800 nm, this balance clamps the filaments intensity to typically 50 TW/cm 2 [11,12]. Filaments cannot be considered as virtual optical fibers guiding the light within their core: they continuously interact and exchange energy with the photon bath surrounding them [13][14][15][16]. This photon bath, also known as energy reservoir [13,17,18], plays a key role in the filamentation process. In particular, the photon bath feeds the filament and balances its energy losses, allowing it to self-heal after an obstacle [14][15][16] or extend its propagation distance [19].In the case of multifilamentation, the laser energy reservoir also mediates interactions between neighboring filaments [20][21][22][23][24][25][26]. This interaction is attractive if the filaments are in phase, and repulsive if they are in antiphase [27,28], corresponding to constructive and destructive interferences in the photon bath, respectively. Previous theoretical and experimental studies have shown that the relative phase between filaments is mainly randomly driven by intensity fluctuations during the collapse [29] and is then stabilized for the filaments propagating after the collapse [30].Recently we showed that at laser powers exceeding 100 TW, this mutual interaction limits the density of filaments in the transverse beam profile [31], resulting in the * corresponding author jean-pi...

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“…As a result, the intensity pattern of an OV beam shows a dark central spot in its cross-section, whose radius increases by increasing the value of topological charge. Spatiotemporal optical vortices (STOV) have been recently introduced as a new class of OAM-carrying light beams whose topological charge has a space-time dependence [22,23]. These beams can physically exist if one could satisfy the condition of noncollinearity between intrinsic OAM and linear momentum, which is L∦P.…”

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confidence: 99%

Time-varying optical vortices enabled by time-modulated metasurfaces

2020

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AbstractIn this paper, generation of optical vortices with time-varying orbital angular momentum (OAM) and topological charge is theoretically demonstrated based on time-modulated metasurfaces with a linearly azimuthal frequency gradient. The topological charge of such dynamic structured light beams is shown to continuously and periodically change with time evolution while possessing a linear dependence on time and azimuthal frequency offset. The temporal variation of OAM yields a self-torqued beam exhibiting a continuous angular acceleration of light. The phenomenon is attributed to the azimuthal phase gradient in space-time generated by virtue of the spatiotemporal coherent path in the interference between different frequencies. In order to numerically authenticate this newly introduced concept, a reflective dielectric metasurface is modelled consisting of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers on top of a mirror-backed silicon slab which renders an electrically tunable guided mode resonance mirror in near-infrared regime. The metasurface is divided into several azimuthal sections wherein nanodisk heterostructures are interconnected via nanobars serving as biasing lines. Addressing azimuthal sections with radio-frequency biasing signals of different frequencies, the direct dynamic photonic transitions of leaky-guided modes are leveraged for realization of an azimuthal frequency gradient in the optical field. Generation of dynamic twisted light beams with time-varying OAM by the metasurface is verified via performing several numerical simulations. Moreover, the role of modulation waveform and frequency gradient on the temporal evolution and diversity of generated optical vortices is investigated which offer a robust electrical control over the number of dynamic beams and their degree of self-torque. Our results point toward a new class of structured light for time-division multiple access in optical and quantum communication systems as well as unprecedented optomechanical manipulation of objects.

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Spatiotemporal Optical Vortices

Cited by 150 publications

References 38 publications

Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

Gas-Solid Phase Transition in Laser Multiple Filamentation

Time-varying optical vortices enabled by time-modulated metasurfaces

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