Rainbow light trapping in plasmonic devices allows for field enhancement of multiple wavelengths within a single device. However, many of these devices lack precise control over spatial and spectral enhancement profiles and cannot provide extremely high localised field strengths. Here we present a versatile, analytical design paradigm for rainbow trapping in nanogroove arrays by utilising both the groove-width and groove-length as tuning parameters. We couple this design technique with fabrication through multilayer thin-film deposition and focused ion beam milling, which enables the realisation of unprecedented feature sizes down to 5 nm and corresponding extreme normalised local field enhancements up to 10³. We demonstrate rainbow trapping within the devices through hyperspectral microscopy and show agreement between the experimental results and simulation. The combination of expeditious design and precise fabrication underpins the implementation of these nanogroove arrays for manifold applications in sensing and nanoscale optics.

等离子体装置中的彩虹光捕获允许单个装置内多个波长的场增强。但是，许多这样的设备缺乏对空间和光谱增强轮廓的精确控制，并且不能提供极高的局部场强。在这里，我们通过利用凹槽宽度和凹槽长度作为调整参数，提出了一种用于纳米凹槽阵列中彩虹捕获的通用分析设计范例。我们将这种设计技术与通过多层薄膜沉积和聚焦离子束铣削进行的制造相结合，从而实现了前所未有的低至5 nm的特征尺寸以及相应的高达10 ^3的极端归一化局部场增强。我们通过高光谱显微镜证明了装置内的彩虹捕获，并表明了实验结果与模拟之间的一致性。快速设计和精确制造的结合为这些纳米凹槽阵列的实现奠定了基础，这些阵列可广泛应用于传感和纳米光学领域。