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Nonlinear spin-orbit conversion via enhanced longitudinal fields in an epsilon-near-zero thin film
We demonstrate how the longitudinal electric field unlocks new possibilities for controlling light's spin and orbital angular momentum in nonlinear harmonic generation. This breakthrough enables the creation of unique vortex harmonics from simple light beams.
Area of Science:
- Optics and Photonics
- Quantum Optics
- Nonlinear Optics
Background:
- Spin-orbit interaction (SOI) of light is crucial for controlling light's spin and orbital angular momentum.
- Conventional methods for nonlinear harmonic generation are limited by symmetry constraints on angular momentum conversion.
Purpose of the Study:
- To investigate the role of the longitudinal electric field in overcoming symmetry limitations in nonlinear harmonic generation.
- To demonstrate experimental observation of nonlinear spin-orbit conversion and generation of phase-singular vortex harmonics.
Main Methods:
- Derivation of general selection rules for angular momentum conversion under longitudinal electric field.
- Enhancement of the longitudinal electric field component at an epsilon-near-zero (ENZ) thin-film interface.
- Experimental generation of second and third-order harmonic vortex beams.
Main Results:
- The longitudinal electric field lifts symmetry constraints on angular momentum conversion without breaking rotational symmetry.
- Nonlinear spin-orbit conversion is made experimentally observable via ENZ interfaces.
- Phase-singular vortex harmonics are generated from a non-singular Gaussian beam.
Conclusions:
- The longitudinal electric field is a critical degree of freedom for controlling angular momentum in harmonic generation.
- This work opens new avenues for structured light generation and manipulation.
- The findings have implications for optical communications, microscopy, and quantum information processing.
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