In this paper, we use a polarization independent phase gradient metasurface to trap sunlight inside a thin film solar cell. In this method, the metasurface is placed at the bottom of the solar cell to anomalously reflect light rays of Sun and prevent them from escaping the cell. The performance of the proposed structure is numerically studied at different wavelengths as well as different angles of incidence, for both TM and TE polarizations. The numerical results show absorption enhancement in a wide range of wavelengths, and short circuit current improvement for both TM and TE polarizations.

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Due to the wave nature of light, the resolution achieved in conventional imaging systems is limited to around half of the wavelength. The reason behind this limitation, called diffraction limit, is that part of the information of the object carried by the evanescent waves scattered from an abject. Although retrieving information from propagating waves is not difficult in the far-field region, it is very challenging in the case of evanescent waves, which decay exponentially as travel and lose their power in the far-field region. In this paper, we design a high-order continuous dielectric metasurface to convert evanescent waves into propagating modes and subsequently to reconstruct super-resolution images in the far field. The designed metasurface is characterized and its performance for sub-wavelength imaging is verified using full wave numerical simulations. Simulation results show that the designed continuous high-order metasurface can convert a large group of evanescent waves into propagating ones. The designed metasurface is then used to reconstruct the image of objects with sub-wavelength features, and an image with the resolution of λ/5.5 is achieved.

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