博士生侯世坤在国际权威期刊Advanced Functional Materials上发表论文

      近日，课题组成员侯世坤同学在刘老师的指导下，以第一作者在国际权威期刊Advanced Functional Materials(影响因子：19.9)上发表题为 “Ferroelectric Interfacial Charge Reconfiguration Programs Excitonic Polarization Anisotropy for Multiplexed Optical Readout ”(铁电界面电荷重构实现激子偏振各向异性的可编程调控与复用光学读出 )的实验论文。

图：铁电界面电荷重构实现激子偏振各向异性的可编程调控与复用光学读出 

         超快通信、安全光子信息交换与量子光网络的快速融合，正在重塑现代信息技术，使高维、本征安全的光学存储与传输从一种理想功能上升为关键需求。与电子载流子相比，光子具有独特优势：其传播过程不存在电阻损耗，同时能够在强度、频率、相位和偏振等多个彼此正交的自由度中编码信息。在这些自由度中，偏振尤为重要，因为它具有本征矢量特性、超快响应能力，并且强烈依赖于探测几何构型。这些特征使偏振域编码成为可重构光学信息处理的有力方案，能够实现超越传统强度探测的复用读出，以及基于检偏器角度选择性的不同信息通道提取。尽管前景广阔，其实际应用仍受到严重限制，关键瓶颈在于缺乏同时具备可逆性、非易失性并可扩展至像素级集成的偏振调制器。现有方法通常依赖缺乏可重构能力的无源光学元件，或依赖需要持续动态偏置的电光/磁光器件，而后者存在易失性、持续功耗以及与纳米尺度架构兼容性较差等问题。 因此，实现微型化、电可重构且非易失的偏振调控单元，仍是发展可扩展偏振复用光学读出的关键挑战。

        过渡金属硫族化合物(TMDs)由于其以激子为主导的光学响应，以及对局域电荷掺杂、对称性破缺和介电屏蔽的高度敏感性，构成了实现偏振光子功能的独特而强大的材料平台。 在这一体系中，由自旋禁戒电子–空穴构型产生的暗激子，相较于亮激子表现出显著抑制的谷退相干和明显延长的寿命。这种长寿命特性使暗激子特别适合承载自旋和谷等矢量自由度，前提是能够引入合适的机制来解锁其光学可访问性。 迄今为止，暗激子的激活与调控主要依赖静电栅控、光泵浦或外加磁场。尽管这些方法能够瞬时访问暗激子态，但其本质上是易失性的：一旦外部激励被移除，激子布居及其相关偏振构型会迅速弛豫，从根本上限制了其在持久光子存储或加密中的应用。面外铁电范德华(vdW)材料为突破这一限制提供了一条决定性路径。其电可切换、能耗低且本征非易失的双稳态极化状态，使其在固态光存储架构中具有重要吸引力。 近期研究表明，铁电极化能够确定性地调控载流子密度和极性，同时调制过渡金属硫族化合物单层中的激子发光强度。 然而，铁电性是否能够主动重构暗激子发射的偏振各向异性，并将这种非易失激子偏振调控进一步转化为图像层面的多角度偏振复用光学读出，目前仍有待探索。

       在此，我们展示了一种基于 WSe₂/CuInP₂S₆(CIPS)异质结构的铁电可重构偏振调制器，实现了用于偏振复用光学读出的激子偏振态非易失写入、切换与保持。铁电切换不仅能够调制激子种类和复合效率，更重要的是，它能够直接重构 WSe₂ 的面内光学各向异性，使发射偏振轴发生约 8° 的确定性旋转。第一性原理计算进一步表明，CIPS 中可逆的 Cu⁺ 位移能够重构界面电荷分布和局域静电环境，在不显著扰动 WSe₂ 类能带色散的情况下，引起与极化相关的带边重新排列和各向异性电荷再分布。基于这一机制，我们进一步提出了双角度偏振复用图像读出的概念验证：利用实验测得的偏振依赖 PL 对比度，在不同偏振检偏角下重构预设图像信息。这些结果建立了一种在 TMDs 异质结构中电可编程、铁电赋能且非易失的激子偏振可重构平台，凸显了其在偏振复用光学读出和集成化偏振分辨光电信息处理中的应用潜力。

文章链接:https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.76831

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Ferroelectric Programming of Excitonic Polarization for Multiplexed Optical Readout

Polarization is one of the most powerful degrees of freedom of light, offering a robust route for encoding, transmitting, and retrieving optical information beyond conventional intensity-based detection. However, practical polarization-domain devices require a combination of properties that is difficult to achieve simultaneously: electrical reconfigurability, nonvolatility, low power consumption, and compatibility with miniaturized photonic architectures. Conventional polarization modulators often rely on passive optical elements or dynamically biased electro-optic and magneto-optic effects, which limit their scalability and introduce continuous power requirements. Developing a compact material platform capable of electrically writing and retaining polarization states therefore remains a key challenge for next-generation optical information processing.

This work demonstrates a ferroelectrically reconfigurable excitonic polarization modulator based on a WSe₂/CuInP₂S₆ (CIPS) van der Waals heterostructure. By integrating monolayer WSe₂ with the out-of-plane ferroelectric semiconductor CIPS, the authors establish a nonvolatile interfacial control mechanism in which the bistable polarization of CIPS programs the excitonic emission anisotropy of WSe₂. Unlike conventional electrostatic gating, which requires a continuous external bias, the ferroelectric polarization state remains after electrical writing, enabling persistent optical modulation without sustained power input.

A central finding of this study is that ferroelectric switching in CIPS does more than modulate the exciton population and emission intensity. It actively reconstructs the in-plane optical anisotropy of monolayer WSe₂, producing a reproducible rotation of the emission polarization axis by approximately 8° between oppositely polarized ferroelectric states. This deterministic polarization rotation provides a direct optical signature of ferroelectric interfacial coupling and establishes a binary, electrically addressable excitonic polarization state. Polarization-resolved photoluminescence measurements reveal clear angular modulation of the emission, while cyclic voltage sweeps show pronounced hysteresis in both excitonic intensity and polarization characteristics, confirming that the effect originates from remanent ferroelectric polarization rather than volatile electrostatic doping.

The work further identifies interfacial charge reconfiguration as the microscopic origin of this programmable excitonic anisotropy. First-principles calculations show that reversible Cu⁺ displacement in CIPS reshapes the interfacial charge landscape and local electrostatic environment at the WSe₂/CIPS interface. Importantly, this process induces polarization-dependent band-edge realignment and anisotropic charge redistribution while largely preserving the intrinsic WSe₂-like band dispersion. Thus, the ferroelectric layer does not simply act as a conventional gate; instead, it provides a nonvolatile interfacial field that modifies the local symmetry and electronic environment experienced by excitons in WSe₂. This mechanism enables a material-state-based route to polarization control that complements geometry-defined nanophotonic platforms such as metasurfaces and plasmonic polarization devices.

Dark excitons play an important role in this platform. Owing to their spin-forbidden nature, long lifetime, and sensitivity to the local electronic environment, dark excitonic states in monolayer WSe₂ offer a favorable channel for hosting and probing polarization anisotropy. The WSe₂/CIPS interface enables ferroelectric control over charged dark-exciton emission, allowing excitonic species, recombination efficiency, and polarization orientation to be electrically modulated. Magneto-optical measurements further distinguish the ferroelectrically programmed linear polarization anisotropy from magnetic-field-induced valley Zeeman splitting, indicating that ferroelectric and magnetic-field control represent largely separable tuning channels.

Beyond fundamental exciton physics, this study demonstrates the potential functionality of the device for polarization-multiplexed optical readout. By using two analyzer angles corresponding to distinct ferroelectrically programmed emission-polarization states, the authors show a conceptual dual-channel image reconstruction scheme. The measured polarization-dependent photoluminescence contrasts are used to retrieve different information channels, demonstrating how nonvolatile excitonic polarization states can be translated into analyzer-angle-selective optical readout. The device also exhibits retention of the programmed polarization state after removal of the bias and maintains resolvable optical modulation after long-term ambient storage and repeated switching, highlighting its promise for nonvolatile polarization photonics.

Overall, this work establishes ferroelectric interfacial charge reconfiguration as a deterministic and nonvolatile mechanism for programming excitonic polarization anisotropy in two-dimensional semiconductor heterostructures. By combining electrically switchable ferroelectricity, exciton-dominated optical response, and polarization-selective readout, the WSe₂/CIPS platform provides a compact foundation for reconfigurable polarization optics, optical memory, and integrated polarization-resolved optoelectronic information processing. The results point toward a broader strategy in which van der Waals ferroelectrics are used not only to tune carrier density, but also to program the vectorial optical response of excitonic materials.