Dual-wavelength metalens enables Epi-fluorescence detection from single molecules

Abstract

Single molecule fluorescence spectroscopy is at the heart of molecular biophysics research and the most sensitive biosensing assays. The growing demand for precision medicine and environmental monitoring requires the creation of miniaturized and portable sensing platforms. However, the need for highly sophisticated objective lenses has precluded the development of single molecule detection systems for truly portable devices. Here, we propose a dielectric metalens device of submicrometer thickness to excite and collect light from fluorescent molecules instead of an objective lens. The high numerical aperture, high focusing efficiency, and dual-wavelength operation of the metalens enable the implementation of fluorescence correlation spectroscopy with a single Alexa 647 molecule in the focal volume. Moreover, the metalens enables real-time monitoring of individual fluorescent nanoparticle transitions and identification of hydrodynamic diameters ranging from a few to hundreds of nanometers. This advancement in sensitivity extends the application of the metalens technology to ultracompact single-molecule sensors.

High Efficiency Triple-Helix Solenoid Beam Generated by Dielectric Metasurface

“…We next discuss the metasurface used to generate the solenoid beam. Metasurfaces, consisting of subwavelength structures engineered to manipulate light, have emerged as powerful tools in optics, demonstrating versatility in various applications such as second and third harmonic generation, − metalenses − and metaholograms. − Recently, metasurfaces have also been used to generate vortex beams, adding to their extensive range of capabilities. − Our metasurface is a Pancharatnam–Berry type (i.e., geometric phase) and based on a-Si nanopillar meta-atoms. Efficient incident beam phase modulation thus requires that the meta-atom should act like a halfwave plate. , A schematic illustration of the meta-atom is shown in Figure a.…”

Metasurfaces for Quantitative Biosciences of Molecules, Cells, and Tissues: Sensing and Diagnostics

“…In addition, studies are being conducted to apply roll-to-roll printing, film insert molding, and injection molding techniques as methods for mass replication of the metasurface . Integration of miniaturized metasurface systems enables arbitrary laser beam steering, fluorescence imaging, and single molecule sensing . Despite these efforts, there are still limitations such as low quality, diffraction limit, material limitations, and efficiency compared to existing technologies and products.…”