Large depth of focus plasmonic metalenses based on Fresnel biprism

Abstract : Plasmonic metalenses are optical elements that are able to shape the amplitude and the phase of light with a high spatial resolution, standing as promising elements for new low-weight imaging technologies. A desired characteristic for metalenses is to have an extended depth of focus (DOF) to bring a larger tolerance of placement of the image plane, reducing image blurring and increasing light directivity. Based on the Fresnel biprism and using the integral equation method, we numerically demonstrate light focusing with cylindrical plasmonic metalenses that are able to generate large DOF values of up to 150λ with transmission efficiencies around 50%. The easiness in the design of our plasmonic metalenses represents an advantage in terms of fabrication, opening new possibilities for the development of small-size lenses for light focusing and imaging applications.