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Second harmonic generation enhancement based on quasi-BICs in centrosymmetric materials
Optics Express
|November 22, 2024
Summary
Researchers designed slotted nanopillar arrays to enhance second-order nonlinear responses in centrosymmetric materials. This design utilizes quasi-bound states in the continuum (quasi-BICs) for efficient light-matter interactions, significantly boosting second harmonic generation (SHG) efficiency.
Area of Science:
- Photonics and Nanotechnology
- Nonlinear Optics
- Materials Science
Background:
- Centrosymmetric optical materials typically exhibit zero second-order nonlinear polarization due to bulk electric dipolar contributions.
- Enhancing nonlinear responses in these materials requires effective utilization of surface terms.
Purpose of the Study:
- To propose and analyze a novel design of densely packed slotted nanopillar arrays for efficient second-order nonlinear responses.
- To investigate the role of quasi-bound states in the continuum (quasi-BICs) in enhancing light-matter interactions and second harmonic generation (SHG).
Main Methods:
- Utilized the finite element method to analyze quasi-BICs in silicon nanopillar arrays.
- Simulated the second harmonic generation (SHG) process under normal-incidence linearly polarized light.
- Investigated the impact of structural parameters (nanopillar radius, lattice constant, slot azimuth) on quasi-BIC properties and SHG efficiency.
Main Results:
- Demonstrated that magnetic dipole-like quasi-BICs with high quality factors are excited, promoting light-matter interactions.
- Showcased that structural parameter adjustments allow wide-range or fine-tuning of resonance wavelength while maintaining high quality factors.
- Achieved significant SHG conversion efficiency (10^-6 ~ 10^-5) and enhancement (10^7 ~ 10^8 times) compared to structures without slots, particularly with optimized slot dimensions.
Conclusions:
- The proposed slotted nanopillar array design effectively enhances second-order nonlinear effects in centrosymmetric materials.
- Quasi-BICs offer a powerful mechanism for modulating resonant wavelengths, quality factors, and nonlinear optical responses.
- This work provides valuable insights for controlling nonlinear effects and developing advanced optical materials.
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