Design and Measurements of a 480 GHz Metamaterial Flat Lens

Abstract

There exist scientifically interesting molecular lines, such as the ground state transitions of water, that cannot be observed except from space. Observations of these lines can be made more cost-effective by lightweighting observation components, such as the primary optical aperture. This is particularly important for SmallSats and CubeSats which have highly limited weight budgets. Here, we present a flat lightweight metamaterial lens, which operates at 480 GHz, close to the 557 GHz ground state transition of ortho–H$_{2}$O. The lens is composed of alternating layers of spin-coated polyimide and patterned aluminum. The aluminum patterning was generated by optimization to a specific phase pattern. We have manufactured and tested the lens. The lens has an optical diameter of 124 mm. It weighs 3 grams and is less than 150 microns thick. It is also flexible. We have demonstrated using a near-field scan that the optical performance of the lens is nearly diffraction-limited. We have found the loss of the lens using radiometric techniques to be 2.5 dB. This loss is roughly 1.5 dB higher than expected, and we investigate possible reasons for this discrepancy.