Imam Safayat-Al, Ishtiak Khandakar Mohammad, Khosru Quazi D M
Opt Express. 2025 Jul 28;33(15):31496-31515. doi: 10.1364/OE.568192.
This study details a tunable and multifunctional terahertz (THz) absorber leveraging the synergistic interaction between phase-transition vanadium dioxide (VO) and adjustable graphene defect layers integrated within aperiodic sequential quasi-photonic structures. Exploiting the phase transition property of VO (insulating to metallic states) and the tunable chemical potential of graphene endows the absorber with dynamically controllable resonance characteristics. The structure shows several high-quality absorption peaks in the 4-6 THz range and a most distinguished one at 4.89 THz in the meantime of VO in the insulating phase. This work reveals strong spectrum tunability of the absorption properties, acted upon separately using heat modulation and alterations in the chemical potential of graphene. Moreover, careful tuning of the Fibonacci defect layer configuration helps to get a very high-quality factor (Q-factor) near 900. Concurrently, the designed structure shows a two-fold increase compared to traditional mono-defect photonics by displaying a large lateral Goos-Hänchen (GH) displacement measured at 389λ. The absorber shows a non-reciprocal feature, achieving unidirectional perfect absorption under forward propagation and no backward absorption, which is an essential requirement for unidirectional energy harvesting. Significantly, the design circumvents the drawbacks of the rigid THz absorbers by incorporating dual tunability (thermal and electrical) and defect engineering. Our optical impedance matched structure ensures near-perfect absorbance (>99%) while demonstrating a clear blue-shifting resonance with defect layer thickness variations. Substantial angular stability (up to 60° of incidence) and polarization insensitivity also add to practicality. Such progress renders these piers an adaptable framework for THz thermal sensing, infrared detection, and energy harvesting, for which tunable spectral regulation and high-Q resonance are beneficial. By uniting the phase-change material functionality, the tunability of graphene, and quasi-periodic defect engineering, the work sets a rubric for a new class of multifunctional nanophotonic devices.
本研究详细介绍了一种可调谐多功能太赫兹（THz）吸收器，该吸收器利用相变二氧化钒（VO）与集成在非周期性顺序准光子结构中的可调谐石墨烯缺陷层之间的协同相互作用。利用VO的相变特性（从绝缘态到金属态）和石墨烯的可调化学势，使该吸收器具有动态可控的共振特性。该结构在4-6太赫兹范围内显示出几个高质量的吸收峰，同时在VO处于绝缘相时，在4.89太赫兹处有一个最为突出的吸收峰。这项工作揭示了吸收特性的强光谱可调性，可分别通过热调制和石墨烯化学势的改变来实现。此外，仔细调整斐波那契缺陷层配置有助于在900附近获得非常高的品质因数（Q因子）。同时，与传统单缺陷光子学相比，所设计的结构通过在389λ处测量到的大横向古斯-汉欣（GH）位移，显示出两倍的提升。该吸收器具有非互易特性，在前向传播时实现单向完美吸收，而反向无吸收，这是单向能量收集的基本要求。值得注意的是，该设计通过结合双可调性（热和电）和缺陷工程，规避了刚性太赫兹吸收器的缺点。我们的光阻抗匹配结构确保了近乎完美的吸收率（>99%），同时随着缺陷层厚度变化呈现出明显的蓝移共振。显著的角度稳定性（高达60°入射角）和偏振不敏感性也增加了实用性。这样的进展使这些结构成为太赫兹热传感、红外探测和能量收集的适应性框架，对于这些应用，可调谐光谱调节和高Q共振是有益的。通过结合相变材料功能特性、石墨烯的可调性和准周期缺陷工程，这项工作为一类新型多功能纳米光子器件设定了标准。
