超高Q值纳米腔中光子-激子-声子的相互作用、相干产生及调控

The generation and control of novel coherent light sources at deep sub-wavelengths scale inevitably require the combination of ultra-high Q nanocavity and high-gain semiconductor luminescent materials. The present application proposes to combine such a high-Q one-dimensional nanobeam cavity and the monolayer two-dimensional transition metal dichalcogenides (TMDs) semiconducting material, to study the interactions among photons, excitons, electrons and phonons in the “nanocaivty-TMDs” coupled system, and to investigate how these interactions would affect the generation and control of the nanoscale optical fields and modes. Due to the strong Coulomb interaction in two-dimensional semiconductors, complex physics processes of excitons take place, including excitons and their complex, and related equilibrium distributions and non-equilibrium dynamics. These are issues of great interests in fundamental physics and are closely related to the hitherto unresolved issue of Mott-transition in the condensed matter physics, which was proposed nearly 70 years ago. They are also critically important to the fundamentally understanding the mechanisms and properties of light emission, especially the coherence properties, of the 2D materials. More importantly, they are essential to the generation and control of novel light sources and their control. The proposed research will entail detailed study on the complex exciton-related physics processes, the strong coupling of excitons and the optical cavity modes, the resonance coupling and the coherent properties of phonons and photons, through the nanoscale photon-phonon cavity, to fully explore the new physics and new effects behind. We anticipate that this project will realize the exciton-polariton lasing, simultaneous or separate phonon and or photon lasing. The realization of these goals would provide solid experimental theoretical foundation for the precise control of nanoscale optical fields in the future.

深亚波长尺度的新型光源的产生和调控不可避免的要求将超高Q-值的纳米腔和最佳的半导体发光材料结合。本申请拟将一维纳米腔和单层二维半导体材料结合，深入研究该系统内光子、激子、电子、声子的相互作用，以及这些相互作用如何影响新型光源和模式的产生和调控。由于二维半导体中很强的库伦力，导致其中复杂的激子物理过程，包括激子及其复合体，它们的平衡分布及非平衡动力学，这些都是目前尚未解决的重大基础物理问题，与近70来凝聚态物理中悬而未决的Mott相变问题紧密相关，对从根本上理解二维材料的发光机理、发光特点、及相干性质至为关键，对未来新型光源的产生和调控关系重大。我们拟通过理论-实验结合来研究这些复杂的激子物理过程、激子与腔模强耦合、声子和光子通过纳米光-声腔的共振耦合、及声子和光子的相干性质等新物理、新效应，以期实现激子极化元激射，声子激射或光-声子同时激射，从而为未来光学模式调控提供实验支撑和理论根据。

本项目将一维纳米腔和单层二维半导体材料结合，深入系统研究该耦合结构中光子、激子、电子、声子的相互作用，以及如何影响新型光源和模式的产生和调控，并取得了一系列国际领先的创新性成果：1）在光子-激子相互作用方面，研究了在不同温度及泵浦条件下二维材料的发光特性，通过调控激子-三子的相互转化和平衡分布，在远低于莫特密度之前实现了超低阈值的三子增益，工作入围2020中国半导体十大研究进展。实验观测到激子的超线性功率依赖行为，最大超线性系数为2.3；首次在无磁场条件下利用栅压调控结构观测到单层MoTe2材料近红外波段的能谷极化荧光，将谷极化寿命从激子的皮秒量级提高到三子的纳秒量级；通过偏振分辨的超快泵浦探测技术首次在二维MoTe2材料中观测到新奇的多体相互作用的光谱特征，结合栅压调控测试和多体理论，阐明光谱特征来源于四体相互作用下的谷间粒子态；实现了介电环境，温度以及应力对二维半导体材料发光的高效调控；2）在光子-电子相互作用方面，提出了一种基于二维材料的场致发光器件结构，无需制备欧姆接触，首次在单层TMDCs发光器件中引入碰撞激发的物理机制；提出并实现了基于WSe2/MoTe2的I-型双异质结近红外发光二极管。与同质PN结相比串联电阻降低了近2个数量级，饱和发光强度提升了30倍。3）在光子-声子相互作用方面，在纳米腔系统中实现了光子与声子的激射，并在此基础之上实现了基于声子激射的高精度片上质量传感，传感精度可达65 zg (6.510-20)。与已报道的质量传感精度结果相比提高了1个数量级以上；设计并制备了光学品质因子2.4×105、光声耦合系数1.02 MHz、声子频率为5.7 GHz的光声微腔，实验上首次实现了全片上的声学奇异点，并实现了一种新型折射率传感器；成功研制世界首个可见光波段高精度的光谱成像芯片，将155216个微型光谱仪集成在一个CMOS图像传感器上，一次拍照即可获得一幅完整的光谱图像，并实现成果转化。

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