Recently, a research group lead by Prof. LIU Hongjun from Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, proposed a novel design of nonlinear metamaterial to enhance the light-matter interactions and breaks through the phase-matching limitations of traditional nonlinear optical parametric processes.
The research results were published in Nanoscale Horizons.
As one of the most promising strategies to achieve nonlinear frequency conversion, metamaterials have demonstrated great significance in detecting Mid-infrared information by frequency up-conversion. Although metamaterials can avoid phase-matching in nonlinear processes, their mechanisms rely on ultrahigh-Q resonances with extremely narrow spectra linewidth that restricted their operation bandwidth.
Therefore, the researchers proposed a hyperbolic metamaterial design, which takes the advantages of electromagnetic multipole coupling supported by gap-plasma modes. The metamaterial is a triangular pyramid shape and it is composed of Au-ZnO multilayer gap.
In specific, the intrinsic modes from triangular metamaterial can induce gap plasma modes, which are of great significance in mode matching. Therefore, the strong field localization at the tip of the triangles can be generated by the symmetry-breaking structure, and eventually excite multiple resonances over a larger spectral range.
Scientists theoretically found that the ultrabroadband mid-infrared nonlinear frequency up-conversion can be achieved in 3 – 5 μm with a pump light at 916 nm. Moreover, the sum frequency process with a maximum conversion efficiency of 2.5 × 105 can be realized using a femtosecond pulsed laser at a pump intensity of 13 MW cm-2.
“The proposed approach provides promising platform for developing ultrabroadband nonlinear coupling of light and matter, and provides a new opportunity for metasurface nonlinear frequency conversion technology,” said Prof. LIU Hongjun.
Fig. The proposed hyperbolic metamaterial and spectra responses. (Image by XIOPM)
(first published: 13 Aug 2024)
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