A broadband approach to sub-diffraction far field imaging and focusing with metamaterials
Geoffroy Lerosey (Institut Langevin, ESPCI ParisTech & CNRS UMR 7587)
In this talk I will show how the use of time dependent and broadband wavefields, in conjunction with metamaterials, permits to beat the diffraction limit from the far field for imaging or focusing purposes. I will introduce the idea of resonant metalens, first demonstrated in the microwave domain, and explain its principles. In particular, I will show how the concept of time reversal can be utilized to focus in this metamaterial based lens and from the far field, onto focal spots much smaller than the diffraction limit. I will then prove the generality of the approach by demonstrating its transposition to the acoustic domain thanks to a very simple setup: an array of soda cans. Then I will present our latest theoretical and numerical results obtained using a resonant metalens made out of plasmonic nanorods in the visible part of the spectrum. I will show that this lens allows, using polychromatic light, to focus light using far field time reversal onto spots as small as 1/30th of the wavelength in the visible. Finally I will prove that our approach can also be used in order to image from the far field and with a subwavelength resolution and could lead to real time sub-diffraction imaging systems.