Chang Xin, Pivnenko Mike, Singh Angadjit, Wu Weijie, Dai Peng, Shrestha Pawan, Chu Daping
Opt Lett. 2024 Oct 1;49(19):5551-5554. doi: 10.1364/OL.537839.
Dynamic metasurface with subwavelength dimensions has emerged as a key optical technology in recent years. Although various active tuning mechanisms are being proposed, liquid crystal-based dynamic metasurface remains attractive due to its large index variation, electrical tunability, reliability, and mass fabricability. In this work, we report a dynamic metasurface for amplitude modulation in reflection, with twisted nematic liquid crystal configuration to reduce broadband reflection in the off state. The metasurface consists of coupled subwavelength grating fingers, which provide alignment for the liquid crystal without the need for an additional alignment material or process. The alignment of liquid crystal materials was examined between crossed polarizers, and the twist of nematic liquid crystal was confirmed. The coupled grating fingers exhibit a resonance quality factor of 27 at telecommunication wavelength and an amplitude modulation depth of 8 times of the minimum at 1630 nm. This work highlights the potential of liquid crystal-based tunable metasurface, combining polarization control via liquid crystal and spectrum control via metasurface. Furthermore, it also shows a way in which the interaction between liquid crystal and metasurface is used for an alignment layer-free cell assembly process.
近年来，具有亚波长尺寸的动态超表面已成为一项关键光学技术。尽管人们提出了各种有源调谐机制，但基于液晶的动态超表面因其较大的折射率变化、电可调性、可靠性和大规模可制造性而仍然具有吸引力。在这项工作中，我们报道了一种用于反射式幅度调制的动态超表面，其采用扭曲向列型液晶配置以减少关态下的宽带反射。该超表面由耦合的亚波长光栅指组成，无需额外的取向材料或工艺即可为液晶提供取向。在正交偏振器之间检查了液晶材料的取向，并确认了向列型液晶的扭曲。耦合光栅指在电信波长处的共振品质因数为27，在1630 nm处的幅度调制深度为最小值的8倍。这项工作突出了基于液晶的可调谐超表面的潜力，它结合了通过液晶进行的偏振控制和通过超表面进行的光谱控制。此外，它还展示了一种利用液晶与超表面之间的相互作用进行无取向层单元组装工艺的方法。
