标题： 所有被动下转换在强度低至 10$^{-7}$ W/cm$^2$的非相干近红外光中的转换 显示英文标题

标题： All-passive upconversion of incoherent near-infrared light at intensities down to 10$^{-7}$ W/cm$^2$

摘要： 频率上转换，即将低能光子转换为高能光子，通常需要强相干照明来驱动非线性过程或使用外部驱动的光电设备。 在这里，我们展示了一个上转换系统，该系统将低强度（低至~10-7 W/cm$^2$）的非相干近红外（NIR）光转换为可见光，达到人眼可感知的强度，而无需任何外部电源输入。 我们的上转换元件由以下成分实现：(1) 通过有机半导体 Y6 和 rubrene 的体异质结中的三重态-三重态湮灭进行光子上转换；(2) 在异质结层中通过等离子增强吸收和场强；(3) 使用二向色性薄膜组件进行收集增强。 为了实现高分辨率成像，上转换元件被插入双波长望远镜系统的中间像平面，该系统保持了入射近红外光和输出可见光之间光线的相对方向性。 我们的全被动上转换成像系统将在能源受限的低光环境中实现近红外成像和传感。 显示英文摘要

摘要： Frequency upconversion, which converts low-energy photons into higher-energy ones, typically requires intense coherent illumination to drive nonlinear processes or the use of externally driven optoelectronic devices. Here, we demonstrate an upconversion system that converts low-intensity (down to ~10-7 W/cm$^2$) incoherent near-infrared (NIR) light into the visible, reaching intensities perceptible by the human eye, without the use of any external power input. Our upconverting element is enabled by the following ingredients: (1) photon upconversion via triplet-triplet annihilation in a bulk heterojunction of the organic semiconductors Y6 and rubrene; (2) plasmonic enhancement of absorption and field intensity in the heterojunction layer; (3) collection enhancement using a dichroic thin-film assembly. To enable high-resolution imaging, the upconverting element is inserted at an intermediate image plane of a dual-wavelength telescope system, which preserves the relative directionality of rays between the incident NIR light and output visible light. Our all-passive upconversion imaging system will enable NIR imaging and sensing in low-light environments under energy constraints.