Planar GRIN Lenses for MEMS Energy Harvesters: A Macroscale Proof of Concept

Phononic Crystal (PnC) Gradient Index (GRIN) lenses have been deeply studied in recent years for their promising applications in energy harvesting. Here, we propose the design and we show an experimental validation of a GRIN lens fully compatible with microfabrication processes that can be employed as Micro-Electro-Mechanical Systems (MEMS) energy harvester after proper miniaturization. Two refractive index gradient formation mechanisms are combined to boost the performances of the lens, thus achieving an amplification factor of 7.49x at the focal point that, to the Authors best knowledge, represents one of thebest results available so far in the context of planar lenses.Numerical simulations and experimental tests performed on a macroscale prototype are in very good agreement.