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Unveiling the propagation dynamics of self-accelerating vector beams

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ABSTRACT

We study theoretically and experimentally the varying polarization states and intensity patterns of self-accelerating vector beams. It is shown that as these beams propagate, the main intensity lobe and the polarization singularity gradually drift apart. Furthermore, the propagation dynamics can be manipulated by controlling the beams’ acceleration coefficients. We also demonstrate the self-healing dynamics of these accelerating vector beams for which sections of the vector beam are being blocked by an opaque or polarizing obstacle. Our results indicate that the self-healing process is almost insensitive for the obstacles’ polarization direction. Moreover, the spatial polarization structure also shows self- healing properties, and it is reconstructed as the beam propagates further beyond the perturbation plane. These results open various possibilities for generating, shaping and manipulating the intensity patterns and space variant polarization states of accelerating vector beams.

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Polarization reconstruction of an RAVB diffracted by an obstacle at the focal plane.In all focal plane panels, the perturbation is denoted by a white, dashed line square, and the polarized transmission axis is denoted by a white arrow. Top row shows the propagation of a radially polarized Airy beam without perturbation is calculated (compare with Fig. 4). 2nd row describes the case where a uniform linear polarizer is applied to the beam at the focal plane. As can be seen, the beam resembles a linearly polarized Airy beam in shape and propagation. Middle row describes the case of a polarization dependent obstacle which is applied at the focal plane, and beam propagation is calculated. From the results it is clear that such an obstacle barely changes the beam’s propagation characteristics, as the propagating beam resembles the non-perturbed case presented in the topmost row. 4th row and bottom row present, the calculated and measured beam propagation beyond an opaque obstacle at the focal plane, respectively. The Stokes parameters of the propagated beam consist of the four-lobe structure typical of radial polarization, which is an indication for polarization reconstruction.
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f5: Polarization reconstruction of an RAVB diffracted by an obstacle at the focal plane.In all focal plane panels, the perturbation is denoted by a white, dashed line square, and the polarized transmission axis is denoted by a white arrow. Top row shows the propagation of a radially polarized Airy beam without perturbation is calculated (compare with Fig. 4). 2nd row describes the case where a uniform linear polarizer is applied to the beam at the focal plane. As can be seen, the beam resembles a linearly polarized Airy beam in shape and propagation. Middle row describes the case of a polarization dependent obstacle which is applied at the focal plane, and beam propagation is calculated. From the results it is clear that such an obstacle barely changes the beam’s propagation characteristics, as the propagating beam resembles the non-perturbed case presented in the topmost row. 4th row and bottom row present, the calculated and measured beam propagation beyond an opaque obstacle at the focal plane, respectively. The Stokes parameters of the propagated beam consist of the four-lobe structure typical of radial polarization, which is an indication for polarization reconstruction.

Mentions: Our experimental results are presented in Figs 2, 3, 4 and 5. Figure 2 presents the intensity distribution and Stokes parameters S1 and S2 of the RAVB at the focal plane and 10 cm beyond the focal plane. We observe experimentally the splitting of the main lobe and the checkerboard pattern of beams’ tail. From observing the Stokes parameters, we notice that the radial polarization structure is indeed imprinted in all the Airy lobes, and the checkers-board structure is the result of destructive interference of anti-phase fields of adjacent lobes. Next, we measured the Stokes parameters of a beam propagating beyond the focal plane, presented in Fig. 2. From these measurements we learn that the change in the beam’s shape is the result of the gradual separation between the radial polarization structure and the Airy pattern. This understanding allows us to study the propagation dynamics of the intensity and polarization of these beams, presented in Figs 3, 4 and 5. As shown in Fig. 3, the radial polarization center is diffracted at the angle expected according to the grating periodicity, whereas the Airy lobes are accelerated and we notice the predicted separation between these structures, i.e. the polarization singularity of the radial beam drifts away from the main lobe towards the RAVB’s tail. This effect is much more pronounced when the acceleration is large, as depicted in Fig. 4, which compares numerically and experimentally between similar beams with a factor of 40 in their acceleration constant. It is seen that for high-acceleration beam (beam A in Fig. 4’s top panels) the separation of the radial polarization and Airy pattern occurs over much shorter distances. Finally, self-healing experiments were made to fully understand the propagation characteristics of RAVBs. These results, alongside with numerical calculations are shown in Fig. 5.


Unveiling the propagation dynamics of self-accelerating vector beams
Polarization reconstruction of an RAVB diffracted by an obstacle at the focal plane.In all focal plane panels, the perturbation is denoted by a white, dashed line square, and the polarized transmission axis is denoted by a white arrow. Top row shows the propagation of a radially polarized Airy beam without perturbation is calculated (compare with Fig. 4). 2nd row describes the case where a uniform linear polarizer is applied to the beam at the focal plane. As can be seen, the beam resembles a linearly polarized Airy beam in shape and propagation. Middle row describes the case of a polarization dependent obstacle which is applied at the focal plane, and beam propagation is calculated. From the results it is clear that such an obstacle barely changes the beam’s propagation characteristics, as the propagating beam resembles the non-perturbed case presented in the topmost row. 4th row and bottom row present, the calculated and measured beam propagation beyond an opaque obstacle at the focal plane, respectively. The Stokes parameters of the propagated beam consist of the four-lobe structure typical of radial polarization, which is an indication for polarization reconstruction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037461&req=5

f5: Polarization reconstruction of an RAVB diffracted by an obstacle at the focal plane.In all focal plane panels, the perturbation is denoted by a white, dashed line square, and the polarized transmission axis is denoted by a white arrow. Top row shows the propagation of a radially polarized Airy beam without perturbation is calculated (compare with Fig. 4). 2nd row describes the case where a uniform linear polarizer is applied to the beam at the focal plane. As can be seen, the beam resembles a linearly polarized Airy beam in shape and propagation. Middle row describes the case of a polarization dependent obstacle which is applied at the focal plane, and beam propagation is calculated. From the results it is clear that such an obstacle barely changes the beam’s propagation characteristics, as the propagating beam resembles the non-perturbed case presented in the topmost row. 4th row and bottom row present, the calculated and measured beam propagation beyond an opaque obstacle at the focal plane, respectively. The Stokes parameters of the propagated beam consist of the four-lobe structure typical of radial polarization, which is an indication for polarization reconstruction.
Mentions: Our experimental results are presented in Figs 2, 3, 4 and 5. Figure 2 presents the intensity distribution and Stokes parameters S1 and S2 of the RAVB at the focal plane and 10 cm beyond the focal plane. We observe experimentally the splitting of the main lobe and the checkerboard pattern of beams’ tail. From observing the Stokes parameters, we notice that the radial polarization structure is indeed imprinted in all the Airy lobes, and the checkers-board structure is the result of destructive interference of anti-phase fields of adjacent lobes. Next, we measured the Stokes parameters of a beam propagating beyond the focal plane, presented in Fig. 2. From these measurements we learn that the change in the beam’s shape is the result of the gradual separation between the radial polarization structure and the Airy pattern. This understanding allows us to study the propagation dynamics of the intensity and polarization of these beams, presented in Figs 3, 4 and 5. As shown in Fig. 3, the radial polarization center is diffracted at the angle expected according to the grating periodicity, whereas the Airy lobes are accelerated and we notice the predicted separation between these structures, i.e. the polarization singularity of the radial beam drifts away from the main lobe towards the RAVB’s tail. This effect is much more pronounced when the acceleration is large, as depicted in Fig. 4, which compares numerically and experimentally between similar beams with a factor of 40 in their acceleration constant. It is seen that for high-acceleration beam (beam A in Fig. 4’s top panels) the separation of the radial polarization and Airy pattern occurs over much shorter distances. Finally, self-healing experiments were made to fully understand the propagation characteristics of RAVBs. These results, alongside with numerical calculations are shown in Fig. 5.

View Article: PubMed Central - PubMed

ABSTRACT

We study theoretically and experimentally the varying polarization states and intensity patterns of self-accelerating vector beams. It is shown that as these beams propagate, the main intensity lobe and the polarization singularity gradually drift apart. Furthermore, the propagation dynamics can be manipulated by controlling the beams’ acceleration coefficients. We also demonstrate the self-healing dynamics of these accelerating vector beams for which sections of the vector beam are being blocked by an opaque or polarizing obstacle. Our results indicate that the self-healing process is almost insensitive for the obstacles’ polarization direction. Moreover, the spatial polarization structure also shows self- healing properties, and it is reconstructed as the beam propagates further beyond the perturbation plane. These results open various possibilities for generating, shaping and manipulating the intensity patterns and space variant polarization states of accelerating vector beams.

No MeSH data available.


Related in: MedlinePlus