Two-photon microscopy with a double-wavelength metasurface objective lens
Two-photon microscopy is a key imaging technique in life sciences due to its superior deep-tissue imaging capabilities. Light-weight and compact two-photon microscopes are of great interest because of their applications for in vivo deep brain imaging. Recently, dielectric metasurfaces have enabled a new category of small and lightweight optical elements, including objective lenses. Here we experimentally demonstrate two-photon microscopy using a double-wavelength metasurface lens. It is specifically designed to focus 820 and 605 nm light, corresponding to the excitation and emission wavelengths of the measured fluorophors, to the same focal distance. The captured two-photon images are qualitatively comparable to the ones taken by a conventional objective lens. Our metasurface lens can enable ultracompact two-photon microscopes with similar performance compared to current systems that are usually based on graded-index-lenses. In addition, further development of tunable metasurface lenses will enable fast axial scanning for volumetric imaging.
© 2018 American Chemical Society. Received: April 28, 2018; Revised: July 12, 2018; Published: July 17, 2018. This work was supported by National Science Foundation Award 1512266. J.L. gratefully acknowledges the financial support from FWO (Flanders). We gratefully acknowledge critical support and infrastructure provided for this work by the Kavli Nanoscience Institute at Caltech. The two-photon microscope was designed and built at the Caltech Neurotechnology Center with support from the Beckman Institute. The authors would like to express thanks for the helpful discussions with Dr. Alon Greenbaum, Dr. Min Jee Jang, and Sripriya Kumar. The authors declare no competing financial interest.
Supplemental Material - nl8b01737_si_001.pdf