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. 2021 Nov 8;11(4):771-778.
doi: 10.1515/nanoph-2021-0493. eCollection 2022 Jan.

Spin to orbital angular momentum transfer in frequency up-conversion

Braian Pinheiro da Silva  1 , Wagner T Buono  2 , Leonardo J Pereira  1 , Daniel S Tasca  1 , Kaled Dechoum  1 , Antonio Z Khoury  1
Affiliations

Spin to orbital angular momentum transfer in frequency up-conversion

Braian Pinheiro da Silva et al. Nanophotonics. .

Abstract

We demonstrate the spin to orbital angular momentum transfer in frequency upconversion with structured light beams. A vector vortex is coupled to a circularly polarized Gaussian beam in noncollinear second harmonic generation under type-II phase match. The second harmonic beam inherits the Hermite-Gaussian components of the vector vortex; however, the relative phase between them is determined by the polarization state of the Gaussian beam. This effect creates an interesting crosstalk between spin and orbital degrees of freedom, allowing the angular momentum transfer between them. Our experimental results match the theoretical predictions for the nonlinear optical response.

Keywords: OAM; nonlinear optics; second harmonic generation; structured light.

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Figures

Figure 1:
Figure 1:
Experimental scheme for spin–orbit angular momentum transfer in second harmonic generation. SP: S-plate for generation of the vector-vortex beam. SLM: spatial light modulator. QWP: Quarter waveplate. HWP: half waveplate. KTP: potassium titanyl phosphate (KTiOPO4) crystal.
Figure 2:
Figure 2:
Images produced on the three outputs of the second harmonic field. Laguerre–Gaussian modes with topological charge ℓ2ω = ±1 are evident in the k1 + k2 beam, as characterized by the spiral and forked interference fringes shown on the right.
Figure 3:
Figure 3:
Hermite–Gaussian modes produced on k1 + k2 by different orientations of the linear polarization prepared on k2.
Figure 4:
Figure 4:
Spin and orbital angular momentum transfer in second harmonic generation with a right circularly polarized k2 beam (S ω = +1), carrying topological charges 0 ≤ ℓ ω ≤ +3 and p = 0. Top row displays the direct image acquisition. Bottom row displays the tilted lens conversion for easy identification of the second harmonic topological charge.
Figure 5:
Figure 5:
Same as Figure 4 for input beam k2 prepared in Laguerre–Gaussian modes with 0 ≤ ℓ ω ≤ 1 and p = 1.
Figure 6:
Figure 6:
Transverse structure before and after the tilted lens.
See this image and copyright information in PMC

References

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