Double-foci acoustic metamaterial Luneburg lens

In this study, an acoustic Luneburg lens is proposed to achieve double foci. High energy density between the two foci can be obtained, which enables the realization of an ultra long acoustic jet between the two foci. The acoustic Luneburg lens is designed based on the gradient index acoustic metamaterial with lattice unit cells. Analytical and numerical analyses were performed to investigate the performance of double foci Luneburg lens. Results show that the double foci can be realized with acoustic jet length goes up to 30 times compared with the wavelength, which has multiple potential applications in medical imaging and energy harvesting.