Comparative analysis of wavefront aberrations between plano-convex lenses and metalenses

Over the past decade, sub-wavelength diffractive optics has emerged as a promising field of research, offering attractive optical characteristics that allow for the manipulation of the amplitude and phase of incident light on flat surfaces. In particular, metalenses have shown strong potential to replace bulk refractive optical elements with ultra-thin planar platforms. In this study, we present a comparative analysis of wavefront aberration between sub-wavelength, nano-sized dielectric metalenses and commercial plano-convex (PCX) lenses at an infrared (IR) wavelength of 1,550 nm. We developed an off-axis interferometry system to observe the point-spread function (PSF) at the focal plane from phase-resolved interference patterns. The phase distribution across the wavefront was observed and calculated using Zernike polynomials. Additionally, we measured the focal spot size, modulation-transfer function (MTF), and Strehl ratio. Through this analysis, we found that the metalenses demonstrate diffraction-limited characteristics and are strongly competitive or even superior to the commercial PCX lenses in most metrics under the designed monochromatic wavelength.