Miniature handheld imaging devices and endoscopes based on coherent Raman scattering are promising for label-free in vivo optical diagnosis. Toward the development of these small-scale systems, a challenge arises from the design and fabrication of achromatic and high-end miniature optical components for both pump and Stokes laser wavelengths. Here, we report a metasurface converting a low-cost plano–convex lens into a water-immersion, nearly diffraction-limited and achromatic lens. The metasurface comprising amorphous silicon nanopillars is designed in a way that all incident rays arrive at the focus with the same phase and group delay, leading to corrections of monochromatic and chromatic aberrations of the refractive lens, respectively. Compared to the case without the metasurface, the hybrid metasurface-refractive lens has higher Strehl ratios than the plano–convex lens and a tighter depth of focus. The hybrid metasurface-refractive lens is utilized in spectroscopic stimulated Raman scattering and coherent anti-Stokes Raman scattering imaging for the differentiation of two different polymer microbeads. Subsequently, the hybrid metalens is harnessed for volumetric coherent Raman scattering imaging of bead and tissue samples. Finally, we discuss possible approaches to integrate such hybrid metalens in a miniature scanning system for label-free coherent Raman scattering endoscopes.

中文翻译：

---

使用近红外消色差超透镜进行相干拉曼散射成像


基于相干拉曼散射的微型手持成像设备和内窥镜有望用于无标记体内光学诊断。在开发这些小型系统时，泵浦和斯托克斯激光波长的消色差和高端微型光学元件的设计和制造面临着挑战。在这里，我们报告了一种超表面，将低成本的平凸透镜转换为水浸式、近衍射极限的消色差透镜。由非晶硅纳米柱组成的超表面的设计方式使得所有入射光线以相同的相位和群延迟到达焦点，从而分别校正折射透镜的单色像差和色像差。与没有超表面的情况相比，混合超表面折射透镜比平凸透镜具有更高的斯特列尔比和更小的焦深。混合超表面折射透镜用于光谱受激拉曼散射和相干反斯托克斯拉曼散射成像，以区分两种不同的聚合物微珠。随后，利用混合超透镜对珠子和组织样本进行体积相干拉曼散射成像。最后，我们讨论了将这种混合超透镜集成到无标记相干拉曼散射内窥镜微型扫描系统中的可能方法。