Diffractive Optics based on metamaterials
A new technology for producing flat optical components based on optical metasurfaces.
These components can potentially serve high resolution imaging, spectrometry, light processing and beam shaping devices. The optical metasurfaces that we develop are composed of closely spaced optical nanoantennas which can be deposited on a wide variety of rigid and flexible surfaces. The engineered nanoantennas allow capturing and directing light at specific colors and polarizations and by that create surfaces with engineered and ‘unnatural’ optical functionality. The active area of the component can be ultrathin allowing in addition to the unique optical properties to reduce the size of the optical components.
Moreover, functionality can be enhanced by creating multilayered components.
The proposed technology can be used to generate a wide variety of novel diffractive optical elements including flat lenses with multispectral and polarization dependent functionality, multifocal components, beam shapers etc. So far we have demonstrated in the lab the use of this technology to correct chromatic aberrations from a diffractive lens and to generate multifunctional laser beam shapers.
Figure 1(a) shows the calculated chromatic aberrations of the focal point using a conventional Fresenel Zone Plate (FZP) and figure 1(b) shows simulation results of focusing light at wavele
ngth of 620 nm and wavelength of 450 nm through a conventional FZP which was designed to focus the light at 620nm to 1mm. It can be seen that light at 450nm is focused further away to ~1.4 mm. The same problem will occur when imaging through such a lens – only one of the wavelengths will be in focus at the image plane. Figure 1(c) shows the simulation results of the focusing properties of a metamaterials based FZP (Meta-FZP). The two wavelengths share the same position of the focal spot which means that chromatic aberrations are corrected. We can use the same technology to correct more than two wavelengths. Fig. 1(d) illustrates this concept.
Figure 1(e) shows a preliminary prototype of a metamaterial based lens that was designed and fabricated at Tel Aviv University nano-center. Fig. 1(f) shows the ability of the meta-FZP to focus blue and yellow light to the same spot by that correcting the chromatic abberations. This shows the first demonstration to our knowledge of chromatic abberation correction by metasurfaces.
In addition to chromatic abberation corrections we demonstrate that this technology can be used for multifunctional laser beam shaping. Fig. 1(g)-(j) present experimental results present experimental results for multifuntional beam shapers which are based on metasurfaces.
The technology can be enhanced also for multispectral manipulation and analysis.