Nonlinear frequency conversion in optical nanoantennas and metasurfaces: materials evolution and fabrication

Abstract

Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics. It has a wide range of applications in our daily lives, including novel light sources, sensing, and information processing. It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect. However, the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems. Therefore, shrinking the nonlinear structures down to the nanoscale, while keeping favourable conversion efficiencies, is of great importance for future photonics applications. In the last decade, researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale, e.g. by employing different nonlinear materials, resonant couplings and hybridization techniques. In this paper, we provide a compact review of the nanomaterials-based efforts, ranging from metal to dielectric and semiconductor nanostructures, including their relevant nanofabrication techniques.

All-metallic wide-angle metasurfaces for multifunctional polarization manipulation

“…Since the electric fields are perpendicular to the vertical axis, E z is forced to vanish at the surface, which helps to reduce the absorption as well as the thermal emission. Interestingly, this coupled plasmonic modes have a feature of catenary optical fields [21][22][23][24] , which provides a universal and useful method for the fast calculating of the optical performance. As shown in our recent work 25 , the semi-analytic description of our current all-metallic structures is possible.…”

Off-axis multi-wavelength dispersion controlling metalens for multi-color imaging

“…By optimizing the geometry size, arrangement and material properties of the sub-wavelength structure, one can flexibly control the amplitude, phase, and polarization of electromagnetic wave 7,8 . Such abilities show their functionalities in various applications, such as nonlinear frequency conversion 9 , vortex beam generation [10][11][12] , holograms [13][14][15] , polarization manipulation 16 , flat lenses [17][18][19] , and virtual shaping [20][21][22][23] , etc. Typically, metasurfaces can reduce the system redundancy, but the chromatic aberration still exists 24 .…”

Controlling plasmon-exciton interactions through photothermal reshaping

“…However, the atomic thickness causes weak optical absorption (<11%) of excitons in monolayer TMDCs, which thereby limits their optoelectronic applications. Fortunately, the metal nanoparticles can facilitate light-matter interactions owing to the surface plasmon resonance, contributing to the enhanced absorption of visible light 25,26 . The surface plasmon can concentrate light beyond the diffraction limit 27 , and that is why metal nanoparticles have been exploited to enhance light-matter interactions in 2D materials.…”