Direct femtosecond laser fabricated photon sieve

Photon sieves, a collection of randomly positioned apertures, focus electromagnetic radiation diffractively and find applications in x-ray optics to astronomy to bio-medical imaging. Femtosecond laser direct writing is an emerging rapid, reliable, and versatile technique for creating diffraction-limited features in dielectrics and metals. Using this technique, we produce localized spots with a modified refractive index within bulk glass and thus fabricate phase photon sieves for optical wavelengths. The distribution of spots was based on numerical simulations. A comparison of the performance of the phase photon sieves and zone-plates created showed a superior performance of the former in terms of tighter focusing and reduction of secondary maxima, thus offering better spatial resolution and imaging capabilities.