Broadband photon sieves imaging with wavefront coding.

A novel method for broadband imaging of using a diffractive photon sieves is proposed and experimentally demonstrated. Unlike conventional photon sieves imaging in which clear imaging is only valid at a single designed wavelength due to the strong wavelength-dependent nature of diffractive elements, broadband photon sieves imaging is implemented with wavefront coding of a simple cubic phase mask without complicated optical system to compensate large chromatic aberration. Experimental validation was performed using an UV-lithography fabricated photon sieves of a focal length of 500mm and a diameter of 50mm at designed wavelength 632.8nm and a diamond-turning fabricated cubic phase mask of a phase parameter α=20π. Results show that extension of the working bandwidth of the proposed photon sieves imaging system is at least 88 times that of a conventional one with almost the same optical resolution and much increased energy efficiency. The proposed method suggests a new concept of extending the applications of photon sieves to work in a broadband wavelength range with a simple method in contrast to conventionally work at a single wavelength only.