Opt Express. 2023 Apr 10;31(8):12789-12801. doi: 10.1364/OE.484137.
Metalenses of adjustable power and ultrathin flat zoom lens system have emerged as a promising and key photonic device for integrated optics and advanced reconfigurable optical systems. Nevertheless, realizing an active metasurface retaining lensing functionality in the visible frequency regime has not been fully explored to design reconfigurable optical devices. Here, we present a focal tunable metalens and intensity tunable metalens in the visible frequency regime through the control of the hydrophilic and hydrophobic behavior of freestanding thermoresponsive hydrogel. The metasurface is comprised of plasmonic resonators embedded on the top of hydrogel which serves as dynamically reconfigurable metalens. It is shown that the focal length can be continuously tuned by adjusting the phase transition of hydrogel, the results reveal that the device is diffraction limited in different states of hydrogel. In addition, the versatility of hydrogel-based metasurfaces is further explored to design intensity tunable metalens, that can dynamically tailor the transmission intensity and confined it into the same focal spot under different states, i.e., swollen and collapsed. It is anticipated that the non-toxicity and biocompatibility make the hydrogel-based active metasurfaces suitable for active plasmonic devices with ubiquitous roles in biomedical imaging, sensing, and encryption systems.
可调功率金属透镜和超薄平面变焦透镜系统作为一种有前途的关键光子器件，在集成光学和先进的可重构光学系统中得到了广泛的应用。然而，在可见频率范围内实现具有透镜功能的主动超表面仍未得到充分探索，以设计可重构光学器件。在这里，我们通过控制独立式热响应水凝胶的亲水性和疏水性行为，在可见频率范围内展示了可调焦金属透镜和可调强度金属透镜。该超表面由嵌入在水凝胶顶部的等离子体激元谐振器组成，用作动态可重构金属透镜。结果表明，通过调整水凝胶的相变可以连续调节焦距，实验结果表明，在水凝胶的不同状态下，该器件具有衍射极限。此外，还进一步探索了基于水凝胶的超表面的多功能性，以设计可调强度的金属透镜，该金属透镜可以在不同状态下，即膨胀和收缩，动态地调整传输强度并将其限制在相同的焦斑内。预计水凝胶基有源超表面的无毒性和生物相容性使其适用于生物医学成像、传感和加密系统等具有普遍应用的有源等离子体器件。
