Liquid crystal integrated metalens with tunable chromatic aberration

Overcoming chromatic aberrations is a vital concern in imaging systems in order to facilitate fullcolor and hyperspectral imaging.By contrast,large dispersion holds opportunities for spectroscopy and tomography.Combining both functions into a single component will significantly enhance its versatility.A strategy is proposed to delicately integrate two lenses with a static resonant phase and a switchable geometric phase separately.The former is a metasurface lens with a linear phase dispersion.The latter is composed of liquid crystals(LCs) with space-variant orientations with a phase profile that is frequency independent.By this means,a broadband achromatic focusing from 0.9 to 1.4 THz is revealed.When a saturated bias is applied on LCs,the geometric phase modulation vanishes,leaving only the resonant phase of the metalens.Correspondingly,the device changes from achromatic to dispersive.Furthermore,a metadeflector with tunable dispersion is demonstrated to verify the universality of the proposed method.Our work may pave a way toward active metaoptics,promoting various imaging applications.