Localized waves carrying orbital angular momentum in optical fibers

Ruano, Paula Nuño; Robson, Charles W.; Ornigotti, Marco

doi:10.1088/2040-8986/abf786

Cited by 7 publications

(3 citation statements)

References 37 publications

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“…Recent theoretical studies have re-examined guided ST supermodes by investigating the potential for synthesizing them within the waveguide itself, either by exploiting time-varying refractive indices to induce indirect photonic transitions from a single waveguide mode to a target guided ST supermode, or through high-energy nonlinear interactions, which may lead to the realization of so-called spatiotemporal “helicon” wave packets after incorporating orbital angular momentum into the field. Another related effort has been to study the propagation of focus-wave modes in optical fibers, and more recently to investigate the impact of the presence of orbital angular momentum on such guided fields …”

Section: Discussionmentioning

confidence: 99%

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Severing the Link between Modal Order and Group Index Using Hybrid Guided Space-Time Modes

Shiri

Abouraddy

2022

ACS Photonics

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The structure of an optical waveguide determines the characteristics of its guided modes, such as their spatial profile and group index. General features are shared by modes regardless of the waveguiding structure; for example, modal dispersion is inevitable in multimode waveguides, every mode experiences group-velocity dispersion, and higher-order modes usually travel at lower group velocities than their lower-order counterparts. We show here that such trends can be fundamentally altered in a multimode planar waveguide by exploiting hybrid guided space-time modes, whereupon dispersion is eliminated and the link between modal order and group index is altogether severed. Hybrid space-time modes are confined in one-dimension by the planar waveguide, and in the other by the underlying spatiotemporal spectral structure of the field itself. Direct measurements of the modal group delays confirm that the group index for low-loss, dispersion-free, hybrid space-time modes can each be tuned away from the group index of the same-order conventional mode, and that the transverse size of these hybrid modes can be varied independently of the modal order and group index. These findings are verified in a few-mode planar waveguide consisting of a 25.5 mm-long, 4-μm-thick silica film deposited on a MgF2 substrate.

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Section: Discussionmentioning

confidence: 99%

“…Another related effort has been to study the propagation of focus-wave modes 63 in optical fibers, 64 and more recently to investigate the impact of the presence of orbital angular momentum on such guided fields. 65…”

Section: ■ Discussionmentioning

confidence: 99%

Severing the Link between Modal Order and Group Index Using Hybrid Guided Space-Time Modes

Shiri

Abouraddy

2022

ACS Photonics

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“…[37] The central characteristics of ST wave packets in free space are now well-understood, [33] and potential applications are being evaluated in optical communications [38] and device physics. [39][40][41][42][43] In contrast to TPFs, the angular dispersion undergirding ST wave packets is "non-differentiable:" the derivative of the propagation angle is not defined at one wavelength. [44] Such angular dispersion can be produced by a recently developed pulsedbeam shaper that serves as a universal angular-dispersion synthesizer in one dimension.…”

Section: Introductionmentioning

confidence: 99%

Canceling and Inverting Normal and Anomalous Group‐Velocity Dispersion Using Space‐Time Wave Packets

Hall

Abouraddy

2022

Laser & Photonics Reviews

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Angular dispersion can counterbalance normal group‐velocity dispersion (GVD) that increases the wave‐vector length in a dispersive medium. By tilting the wave vector, angular dispersion reduces the axial wave number in this case to match the pre‐GVD value. By the same token, however, angular dispersion fails to counterbalance anomalous GVD, which in contrast reduces the wave‐vector length. Consequently, GVD‐cancellation via angular dispersion has not been demonstrated to date in the anomalous dispersion regime. Here, structed femtosecond pulsed beams, known as ‘space‐time’ wave packets, are designed to realize dispersion‐cancellation symmetrically in either the normal‐ or anomalous‐GVD regimes by virtue of non‐differentiable angular dispersion inculcated into the pulsed field. Furthermore, GVD‐inversion is also verified by reversing the GVD sign experienced by the field with respect to that dictated by the chromatic dispersion of the medium itself.

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Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons

et al. 2023

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Because surface plasmon polaritons (SPPs) are surface waves characterized by one free transverse dimension, the only monochromatic diffraction-free spatial profiles for SPPs are cosine and Airy waves. Pulsed SPP wave packets have been recently formulated that are propagation-invariant and localized in the in-plane dimensions by virtue of a tight spectral association between their spatial and temporal frequencies, which have thus been dubbed "space-time" (ST) SPPs. Because of the spatiotemporal spectral structure unique to ST-SPPs, the optimal launching strategy of such novel plasmonic field configurations remains an open question. We present here a critical step toward realizing ST-SPPs by reporting observations of ultrabroadband striped ST-SPPs. These are SPPs in which each wavelength travels at a prescribed angle with respect to the propagation axis to produce a periodic (striped) transverse spatial profile that is diffraction-free. We start with a free-space ST wave packet that is coupled to a ST-SPP at a gold-dielectric interface, and unambiguously identify the ST-SPP via an axial beating detected in two-photon fluorescence produced by the superposition of incident ST wave packet and the excited surface-bound ST-SPP. These results highlight a viable approach for efficient and reliable coupling to ST-SPPs and, thus, represent the first crucial step toward realization of the full potential of ST-SPPs for plasmonic sensing and imaging.

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Localized waves carrying orbital angular momentum in optical fibers

Cited by 7 publications

References 37 publications

Severing the Link between Modal Order and Group Index Using Hybrid Guided Space-Time Modes

Severing the Link between Modal Order and Group Index Using Hybrid Guided Space-Time Modes

Canceling and Inverting Normal and Anomalous Group‐Velocity Dispersion Using Space‐Time Wave Packets

Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons

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