All-optical fabrication of 2D and 3D photonic structures using a single polymer phase mask

A novel method is presented for the fabrication of 2D and 3D structures based on single beam exposure through a phase mask. The thin film mask consists of three phase gratings arranged in plane equilateral triangle geometry with grating vectors at 120 degrees. to each other. In the first step the gratings were inscribed into a film of an azobenzene containing polymer using polarization holography. The resulting complex surface relief holographic element was then duplicated into a transparent colourless surface relief element by soft lithography. 2D and 3D surface relief and volume photonic elements were fabricated by a single laser beam exposure (at UV or visible wavelengths depending on the material) through this colourless mask. Azobenzene containing materials and photopolymers, including organic-inorganic nanocomposites, were used as holographic materials. In this way an easily fabricated and cheap phase 'photonic' mask, with much higher diffraction efficiency compare to an amplitude mask, has been proposed and realized. Moreover, the method offers a control over the parameters of the resulting 2D and 3D structures (periods from sub-micrometres to a few micrometres) by changing the parameters of the gratings in the first optical element inscribed in the azobenzene polymer film. The technique has been used for one-step manufacture of hexagonal surface relief gratings, then used for layer-by-layer photonic structures.