Manipulating the transverse spin angular momentum and Belinfante momentum of spin-polarized light by a tilted stratified medium in optical tweezers

Roy, Sauvik; Ghosh, Nirmalya; Banerjee, Ayan; Gupta, Subhasish Dutta

doi:10.1103/physreva.105.063514

Cited by 5 publications

(2 citation statements)

References 29 publications

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“…The small shift is probably related to the paraxially incident beam that we have used. A highly focused non-paraxial beam has been shown to show strong SOI effects: for example, beams tightly focused by high-numerical-aperture lenses [4,54,55] or scattered by small particles [2,56]. Moreover our system supports BIC only for p-polarized light, since s-polarized light cannot excite the Berreman modes.…”

Section: Resultsmentioning

confidence: 99%

Enhanced beam shifts mediated by bound states in continuum

Biswas

Remesh

Achanta

et al. 2023

J. Opt.

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The interaction of light beams with resonant structures has led to the development of various optical platforms for sensing, particle manipulation, and strong light-matter interaction. In the current study, we investigate the manifestations of the bound states in continuum (BIC) on the in plane and out of plane shifts (referred to as Goos-Hanchen (GH) and Imbert-Fedorov (IF) shifts, respectively) of a finite beam with specific polarization incident at an arbitrary angle. Based on the angular spectrum decomposition, we develop a generic formalism for understanding the interaction of the finite beam with an arbitrary stratified medium with isotropic and homogeneous components. it is applied to the case of a Gaussian beam with p and circularly polarized light incident on a symmetric structure containing two polar dielectric layers separated by a spacer layer. For p-polarized plane wave incidence one of the coupled Berreman modes of the structure was recently shown to evolve to the bound state with infinite localization and diverging quality factor coexisting with the other mode with large radiation leakage (Remesh et al. Optics Communications, 498:127223, 2021). A small deviation from the ideal BIC resonance still offers resonances with very high quality factors and these are exploited in this study to report giant GH shifts. A notable enhancement in the IF shift for circularly polarized light is also shown. Moreover, the reflected beam is shown to undergo distortion leading to a satellite spot. The origin of such a splitting of the reflected beam is traced to a destructive interference due to the left and right halves of the corresponding spectra.

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Section: Resultsmentioning

confidence: 99%

Enhanced beam shifts mediated by bound states in continuum

Biswas

Remesh

Achanta

et al. 2023

J. Opt.

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“…In the non-paraxial regime, though, the longitudinal component of electric/magnetic field is considerably enhanced due to the effects of SOI, which increases the magnitude of TSAM correspondingly. [11][12][13] While TSAM has been studied in detail in theory, [14][15][16][17] experimental evidence has been obtained mostly in the case of evanescent fields, in the form of rotation of dielectric particles. [18][19][20] However, obtaining TSAM signatures for propagating fields is difficult to obtain experimentally, since these are often conjugated with those due to LSAM, leading to complex rotational motion in the probe particles.…”

Section: Introductionmentioning

confidence: 99%

Probing Dual Asymmetric Transverse Spin Angular Momentum in Tightly Focused Vector Beams in Optical Tweezers

Kumar,

Nayak,

Gupta

et al. 2023

Laser & Photonics Reviews

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The spin‐orbit interaction (SOI) of light generated by tight focusing in optical tweezers is regularly employed in generating angular momentum ‐ both spin and orbital ‐ the effects being extensively observed in trapped mesoscopic particles. Specifically, the transverse spin angular momentum (TSAM), which arises due to the longitudinal component of the electromagnetic field generated by tight focusing is of special interest, both in terms of fundamental studies and associated applications. This study provides an effective and optimal strategy for generating TSAM in optical tweezers by tightly focusing first‐order radially and azimuthally polarized vector beams with no intrinsic angular momentum (AM) into a refractive index stratified medium. The choice of such input fields ensures that the longitudinal spin angular momentum (LSAM) arising from the electric (magnetic) field for the radial (azimuthal) polarization is zero. As a result, the effects of the electric and magnetic TSAM are exclusively observed separately in the case of input first‐order radially and azimuthally polarized vector beams on single optically trapped birefringent particles. This research opens up new and simple avenues for exotic and complex particle manipulation in optical tweezers.

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