Coherent Raman scattering imaging with a near-infrared achromatic metalens

Abstract

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.

Wide field-of-view metalens: a tutorial

“…More recently, the same group developed a bijective metalens configuration to circumvent the classical trade-off between resolution and depth of field in tomography imaging 136 . Coherent Raman scattering and stimulated emission depletion endoscopic imaging based on metalenses have also been explored 137 , 138 . Emerging techniques facilitating integration of metasurfaces on fiber facets also envisage novel miniaturized endoscopic probes with enhanced and versatile imaging capabilities 139 …”

Design of Novel Optical Cavities for Strong Shock Compression

“…3. This array can then be transformed into multiple rings at the sample surface, by sequentially passing through either a refractive axicon array or an axicon array phase object [14,15], and then through focusing optics. Since all the beams transmitted through the axicon array are all collinear, a single conventional focusing element can be used to form concentric rings at the sample location.…”

Achromatic and Coma-Corrected Hybrid Meta-Optics for High-Performance Thermal Imaging

“…To overcome the above-mentioned restrictions and advance practical high-performance imaging applications, several hybrid metalens doublets composed of a large-scale metasurface aberration corrector and a refractive lens are theoretically or experimentally demonstrated for continuous achromatic focusing or imaging in the visible − and near-infrared − regions at normal incidence. However, due to the existent monochromatic aberrations such as coma, their FOV angles are limited.…”