Noh Heeso, Popoff Sébastien M, Cao Hui
Department of Applied Physics, Yale University, New Haven, CT 06520, USA.
Opt Express. 2013 Jul 29;21(15):17435-46. doi: 10.1364/OE.21.017435.
Optical absorption is usually considered deleterious, something to avoid if at all possible. We propose a broadband nanoabsorber that completely eliminates the diffracting wave, resulting in a subwavelength enhancement of the field. Broadband operation is made possible by engineering the dispersion of the complex dielectric function. The local enhancement can be significantly improved compared to the standard plane wave illumination of a metallic nanoparticle. Our numerical simulation shows that an optical pulse as short as 6 fs can be focused to a 11 nm region. Not only the local field, but also its gradient are greatly enhanced, pointing to applications in ultrafast nonlinear spectroscopy, sensing and communication with deep-subwavelength resolution.
光吸收通常被认为是有害的，若有可能应尽量避免。我们提出了一种宽带纳米吸收体，它能完全消除衍射波，从而实现场的亚波长增强。通过设计复介电函数的色散实现了宽带工作。与金属纳米颗粒的标准平面波照明相比，局部增强效果可得到显著改善。我们的数值模拟表明，短至6飞秒的光脉冲可聚焦到11纳米的区域。不仅局部场，而且其梯度也大大增强，这表明该技术可应用于具有深亚波长分辨率的超快非线性光谱、传感和通信领域。
