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Second Harmonic Generation due to the Spatial Structure of a Radiation Beam
A A Gunyaga1, M V Durnev1, S A Tarasenko1
1Ioffe Institute, 194021 St. Petersburg, Russia.
Physical Review Letters
|May 2, 2025
Summary
Spatially structured light generates a second harmonic in simple media due to nonlocal electric response. This new mechanism for second harmonic generation and light structuring bypasses crystal symmetry limitations.
Area of Science:
- Nonlinear optics
- Condensed matter physics
- Photonics
Background:
- Second harmonic generation (SHG) typically requires non-centrosymmetric materials.
- Structured light possesses spatial variations in its intensity, phase, or polarization.
- The electric response of a medium can exhibit nonlocality, depending on fields beyond the immediate point of interaction.
Purpose of the Study:
- To demonstrate second harmonic generation in homogeneous and isotropic media using spatially structured radiation.
- To develop an analytical theory for this novel SHG mechanism.
- To explore the implications for light structuring and angular momentum transfer.
Main Methods:
- Analytical theory development for second harmonic generation in conducting two-dimensional systems.
- Calculation of electric currents and emitted radiation at double the frequency for general structured light.
- Application of the theory to twisted light beams.
Main Results:
- Spatially structured radiation induces second harmonic generation even in homogeneous and isotropic media.
- The effect is attributed to the nonlocality of the electric response to structured electromagnetic fields.
- For twisted light, the theory predicts a doubling of the light's angular momentum in the second harmonic emission.
Conclusions:
- A new pathway for second harmonic generation and light structuring has been established, independent of crystal symmetry.
- Nonlocal electric response to structured light is a key mechanism for nonlinear optical phenomena.
- This work opens possibilities for advanced optical control and manipulation of light.
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