近日，英国诺丁汉特伦特大学的Lei Xu&Mohsen Rahmani及其研究团队取得一项新进展。经过不懈努力，他们实现介质超表面中导模共振控制的宽带红外成像。相关研究成果已于2024年9月10日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队通过引入一种新型非线性成像平台解决了这一问题，该平台利用泵浦光束通过四波混频（FWM）来增强信号转换，其中超表面在泵浦波长而非信号或非线性发射波长处产生共振。因此，研究人员展示了利用超表面对任意物体进行宽带非线性成像的能力。

研究人员引入了一种硅基盘状超表面，其在泵浦波长处具有可激发的导模共振，从而实现了从超过1000纳米到4000纳米的宽红外图像直接转换为可见光。

重要的是，采用FWM通过利用泵浦光束强度与信号转换效率之间的二次关系，显著降低了对高功率信号输入或在信号光束处具有共振特征的非线性成像的依赖。因此，这项研究成果释放了超表面在宽带红外成像方面的潜力，为下一代采用芯片级光子器件的全光红外成像技术带来了有希望的进步。

据悉，非线性超表面因其在红外成像和光谱学等多种应用中的潜力而近期迅速发展。然而，由于超表面的转换效率较低，已采用多种策略来提升其性能，包括在信号或非线性发射波长处利用共振效应。这一策略导致非线性超表面的工作频段变窄，进而对非线性全息术、图像编码及非线性超透镜等诸多应用构成了瓶颈。

附：英文原文

Title: Broadband infrared imaging governed by guided-mode resonance in dielectric metasurfaces

Author: Zheng, Ze, Smirnova, Daria, Sanderson, Gabriel, Cuifeng, Ying, Koutsogeorgis, Demosthenes C., Huang, Lujun, Liu, Zixi, Oulton, Rupert, Yousefi, Arman, Miroshnichenko, Andrey E., Neshev, Dragomir N., ONeill, Mary, Rahmani, Mohsen, Xu, Lei

Issue&Volume: 2024-09-10

Abstract: Nonlinear metasurfaces have experienced rapid growth recently due to their potential in various applications, including infrared imaging and spectroscopy. However, due to the low conversion efficiencies of metasurfaces, several strategies have been adopted to enhance their performances, including employing resonances at signal or nonlinear emission wavelengths. This strategy results in a narrow operational band of the nonlinear metasurfaces, which has bottlenecked many applications, including nonlinear holography, image encoding, and nonlinear metalenses. Here, we overcome this issue by introducing a new nonlinear imaging platform utilizing a pump beam to enhance signal conversion through four-wave mixing (FWM), whereby the metasurface is resonant at the pump wavelength rather than the signal or nonlinear emissions. As a result, we demonstrate broadband nonlinear imaging for arbitrary objects using metasurfaces. A silicon disk-on-slab metasurface is introduced with an excitable guided-mode resonance at the pump wavelength. This enabled direct conversion of a broad IR image ranging from >1000 to 4000nm into visible. Importantly, adopting FWM substantially reduces the dependence on high-power signal inputs or resonant features at the signal beam of nonlinear imaging by utilizing the quadratic relationship between the pump beam intensity and the signal conversion efficiency. Our results, therefore, unlock the potential for broadband infrared imaging capabilities with metasurfaces, making a promising advancement for next-generation all-optical infrared imaging techniques with chip-scale photonic devices.

DOI: 10.1038/s41377-024-01535-w

Source: https://www.nature.com/articles/s41377-024-01535-w