Focusing a beam beyond the diffraction limit using a hyperlens-based device

摘要

A super-focusing device composed of a focusing objective and a hyperlens is proposed to focus an incident plane wave into the deep subwavelength dimension.In the device,the objective converts the incident plane wave into a convergent one.The half cylindrical hyperlens can support high wave vector k modes propagating towards its core.So the convergent wave can be focused into an ultrasmall spot beyond the diffraction limit.The layout is proposed for the super-focusing device and its characteristics are investigated theoretically.Numerical simulations verify that the focused beams are confined in a spot with a diameter of 16.3 nm in the focal plane of the focusing objective with a numerical aperture of 0.6,which corresponds to a super-resolution spot of Ao/23(Ao is the wavelength in vacuum).The simulations confirm the effectiveness of the proposed device.