Manipulating continuous optical spectra in the wave vector domain by metalens

Complete 2π cycling of a phase around a phase singularity leads to a rapid phase variation in the nearby zones and forms a sharp local <i>k</i>-vector peak. In this paper, the intensity distribution in the spatial domain is transformed into a <i>k</i>-vector distribution in the wave vector domain, and we prove that the local <i>k</i>-vector peak is generated at the point of minimum light field intensity. The local <i>k</i>-vector peak is sharper when the minimum point is closer to the phase singularity. The <i>k</i>-vector peak can be manipulated by controlling the minimum optical field intensity. A metalens is designed to generate sharp <i>k</i>-vector peaks for continuous wavelengths and linearly shift the positions of these peaks with the incident wavelength. This method transforms full-band continuous optical spectra from the spatial domain to the wave vector domain. The spectral resolutions over the wavelength range from 800 nm to 810 nm are less than 0.82 nm, and the optimal spectral resolution reaches 0.027 nm. This approach can be used in metasurface spectroscopy, providing what we believe to be a new way to improve spectral resolution.