Holographic optics for increased detection efficiency

We have proposed, designed, simulated and fabricated a holographic, low loss focusing lens with engineered nano-scaled features. This metastructure was designed to converge off-axis infrared (IR) radiation and created by patterning a dielectric surface. To leverage previous efforts for baseline data, we chose an array of nano-pillars which varied in widths although were fixed in both height and periodicity. We achieved the desired Gradient Index (GRIN) and resulting focus length, by engineering the effective index of refraction across the metasurface which was achieved from varying the material-to-air ratio. This allowed us to create a parabolic phase gradient, thereby generating an effective optical density that peaks in the appropriate sector of the lens while gradually degrading towards the perimeter of the lens in Figure 1. Lenslets with varying patterns, dependent upon their position in the array, were designed, simulated and fabricated.