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Theoretical design of the nonlinear Janus metastructure based on second harmonic generation with difference
Xiang Li1, Cheng Yang1, Chu-Ming Guo1
1The other authors are with College of Electronic and Optical Engineering and the College of Flexible Electronics (Future Technology), Nanjing University of Posts and Telecommunications, Nanjing, 210023, China.
Nanoscale
|September 26, 2025
Summary
This study introduces a nonlinear Janus metastructure for enhanced second harmonic generation (SHG). It enables precise angle detection and sensing of material thickness and refractive index.
Area of Science:
- Nonlinear optics
- Metamaterials
- Nanophotonics
Background:
- Second harmonic wave (SHW) generation is a key nonlinear optical effect.
- Nonlinear superstructures are crucial for advanced optical devices.
Purpose of the Study:
- To propose and investigate a nonlinear Janus metastructure (NJM) for enhanced SHG.
- To explore SHG in both forward and backward directions using quasi-phase matching.
- To demonstrate applications in angle detection, thickness sensing, and refractive index measurement.
Main Methods:
- Utilized quasi-phase matching for second harmonic generation (SHG).
- Investigated a one-dimensional nonlinear Janus metastructure (NJM) based on lithium-tantalate-crystal modulation.
- Employed peak frequency (PF) difference for angle detection and peak output (OP) variation for sensing.
Main Results:
- Observed groundbreaking enhancement of forward and backward SHW within the NJM under phase matching conditions.
- Demonstrated effective PF difference detection in an angle range of 5° to 9°.
- Achieved thickness sensing from 160 nm to 180 nm and RI measurement within 1.55-1.65 and 1.70-1.80 ranges.
Conclusions:
- The NJM effectively enhances SHG.
- The proposed methods provide precise detection capabilities for angles, thickness, and refractive index.
- This work offers insights for designing differential electromagnetic detection devices.
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