Imaging through nonlinear metalens using second harmonic generation

TL;DR

This paper demonstrates the use of nonlinear metalenses for imaging via second harmonic generation, enabling infrared imaging with visible detectors and dynamic control of image formation.

Contribution

It introduces nonlinear metalenses that combine imaging and frequency conversion, allowing for switchable real or virtual images and nonlinear optical modulation.

Findings

Successful imaging of objects with near-infrared light in the second harmonic visible range

Ability to switch between real and virtual images by changing polarization handedness

Nonlinear metalenses enable infrared imaging with visible detectors and nonlinear optical responses

Abstract

The abrupt phase change of light at metasurfaces provides high flexibility in wave manipulation without the need of accumulation of propagating phase through dispersive materials. In the linear optical regime, one important application field of metasurfaces is imaging by planar metalenses, which enables device miniaturization and aberration correction compared to conventional optical microlens systems. With the incorporation of nonlinear responses into passive metasurfaces, optical functionalities of metalenses are anticipated to be further enriched, leading to completely new applications areas. Here, we demonstrate imaging with nonlinear metalenses that combine the function of an ultrathin planar lens with simultaneous frequency conversion. With such nonlinear metalenses, we experimentally demonstrate imaging of objects with near infrared light while the image appears in the second harmonic signal of visible frequency range. Furthermore, the functionality of these nonlinear metalenses can be modified by switching the handedness of the circularly polarized fundamental wave, leading to either real or virtual nonlinear image formation. Nonlinear metalenses do not only enable infrared light imaging through a visible detector but also have the ability to modulate nonlinear optical responses through an ultrathin metasurface device while the fundamental wave remains unaffected, which offers the capability of nonlinear information processing with novel optoelectronic devices.