Guo Qiushi, Esin Iliya, Li Cheng, Chen Chen, Han Guanyu, Liu Song, Edgar James H, Zhou Selina, Demler Eugene, Refael Gil, Xia Fengnian
Department of Electrical and Computer Engineering, Yale University, New Haven, CT, USA.
Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, USA.
Nature. 2025 Mar;639(8056):915-921. doi: 10.1038/s41586-025-08686-9. Epub 2025 Mar 19.
Phonon polaritons are quasiparticles resulting from the coherent coupling of photons with optical phonons in polar dielectrics. Owing to their exceptional ability to confine electric fields to deep-subwavelength scales with low loss, they are uniquely poised to enable a suite of applications beyond the reach of conventional photonics, such as subdiffraction imaging and near-field energy transfer. The conventional approach to exciting phonon polaritons through optical methods, however, involves costly light sources along with near-field schemes, and generally leads to low excitation efficiency owing to substantial momentum mismatch between phonon polaritons and free-space photons. Here we demonstrate that under proper conditions, phonon polaritons can be excited all-electrically by drifting charge carriers. Specifically, in hexagonal boron nitride (hBN)/graphene heterostructures, by electrically driving charge carriers in ultrahigh-mobility graphene out of equilibrium, we observe bright electroluminescence of hBN's hyperbolic phonon polaritons (HPhPs) at mid-infrared frequencies, which shows a temperature and carrier density dependence distinct from black-body thermal emission. Moreover, the carrier density dependence of the HPhP electroluminescence spectra reveals that HPhP electroluminescence can arise from both interband transition and intraband Cherenkov radiation of charge carriers in graphene. The HPhP electroluminescence offers avenues for realizing electrically pumped mid-infrared and terahertz phonon-polariton light sources.
声子极化激元是由光子与极性电介质中的光学声子相干耦合产生的准粒子。由于它们具有将电场限制在深亚波长尺度且损耗低的卓越能力，它们特别适合实现一系列传统光子学无法企及的应用，如亚衍射成像和近场能量转移。然而，通过光学方法激发声子极化激元的传统方法涉及昂贵的光源以及近场方案，并且由于声子极化激元和自由空间光子之间存在巨大的动量失配，通常导致激发效率较低。在此，我们证明在适当条件下，声子极化激元可以通过漂移电荷载流子全电学方式激发。具体而言，在六方氮化硼（hBN）/石墨烯异质结构中，通过将超高迁移率石墨烯中的电荷载流子电驱动至非平衡状态，我们在中红外频率下观测到hBN的双曲线声子极化激元（HPhP）的明亮电致发光，其呈现出与黑体热辐射不同的温度和载流子密度依赖性。此外，HPhP电致发光光谱的载流子密度依赖性表明，HPhP电致发光可源自石墨烯中电荷载流子的带间跃迁和带内切伦科夫辐射。HPhP电致发光为实现电泵浦中红外和太赫兹声子极化激元光源提供了途径。
