Electrically switchable phase-type fractal zone plates and fractal photon sieves.

Electrically switchable phase-type fractal zone plates and fractal photon sieves were fabricated using polymer-dispersed liquid crystal material based on a photomask. While both exhibited similar first-order diffraction behavior, the fractal photon sieves showed greatly suppressed diffraction at higher orders. Compared with current amplitude-type photomasks, our switchable, phase-type devices demonstrated higher diffraction efficiency, an important factor in the future development of adaptive optics.