image: a Designed structures with VO2, HfO2, Si multilayers for reversible manipulation in the VIS, IR, THz and MW regions. From top to bottom, the thickness range for these layers are VO2 (500 nm)/ HfO2 (depends on the requirement)/ Si (150 nm)/ VO2 (0–60 nm)/ HfO2 (0–100 nm)/ VO2 (0–20 nm); b Transformation of crystal and band structures during the phase transition of VO2; c The ideal spectrum of the proposed optical system ranging from VIS to MW regions, is drawn based on the measured spectra. The solid lines represent the spectra for VO2(M), and the dashed lines represent the spectra for VO2(R); It should be mentioned that the metallic VO2(R) induces the perfect absorption in IR, and the absorption wavelength can be dynamically modulated by structural parameters; d The comparison of covering bands, response time and energy consumption of different references. The spectral span is the ratio of the maximum and minimum wavelength of the dynamic control region
Credit: by Hang Wei, Jinxin Gu, Tao Zhao, Zhiyuan Yan, He-Xiu Xu, Shuliang Dou, Cheng-Wei Qiu, and Yao Li
Optical materials capable of dynamically manipulating electromagnetic waves are an emerging field in memories, optical modulators, and thermal management. Recently, their multispectral design preliminarily attracts much attention, aiming to enhance their efficiency and integration of functionalities. However, the multispectral manipulation based on these materials is challenging due to their ubiquitous wavelength dependence restricting their capacity to narrow wavelengths.
In a new paper published in Light Science & Application, a team of scientists, led by Professor Yao Li from Center for Composite Materials and Structure, Harbin Institute of Technology, Professor Cheng-Wei Qiu from National University of Singapore, and co-workers cascade multiple tunable optical cavities with selective-transparent layers, enabling a universal approach to overcoming wavelength dependence and establishing a multispectral platform with highly integrated functions. Based on it, they demonstrate the multispectral (ranging from 400 nm to 3 cm), fast response speed (0.9 s), and reversible manipulation based on a typical phase change material, vanadium dioxide (VO2). The platform involves tandem VO2-based Fabry-Pérot (F-P) cavities enabling the customization of optical responses at target bands independently. It can achieve broadband color-changing capacity in the visible region (a shift of ~60 nm in resonant wavelength) and is capable of freely switching between three typical optical models (transmittance, reflectance, and absorptance) in the infrared to microwave regions with drastic amplitude tunability exceeding 0.7. Moreover, the ultrafast phase transition of VO2 enables faster response time of 0.9 s compared to electrochromic materials-based systems.
Journal
Light Science & Applications