Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light–m... more Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light–matter interaction based on multipolar resonances and plasmonics, hence offering the great capability of empowering nonlinear generation. Recently, owing to their ability to manipulate the amplitude and phase of the nonlinear emission in the subwavelength scale, metasurfaces have been recognized as ultra-compact, flat optical components for a vast range of applications, including nonlinear imaging, quantum light sources, and ultrasensitive sensing. This review focuses on the recent progress on nonlinear metasurfaces for those applications. The principles and advances of metasurfaces-based techniques for image generation, including image encoding, holography, and metalens, are investigated and presented. Additionally, the overview and development of spontaneous photon pair generation from metasurfaces are demonstrated and discussed, focusing on the aspects of photon pair generation rate an...
We develop a new approach based on quasi-BICs to develop chiral metasurfaces exhibiting nonlinear... more We develop a new approach based on quasi-BICs to develop chiral metasurfaces exhibiting nonlinear circular dichroism (up to 99.9%) and high conversion efficiency. Tuning mode interference allows selective linear and nonlinear circular dichroism.
A new branch of nonlinear nanophotonics based on high refractive index dielectric nanoparticles i... more A new branch of nonlinear nanophotonics based on high refractive index dielectric nanoparticles is emerging [1]. The unique large resonant enhancement of both electric and magnetic fields associated with very low dissipative losses considerably increases optical interactions at sub-wavelength scales opening new unexplored functionalities. Recently, AlGaAs nanodisks enabled second harmonic generation (SHG) from a near-infrared pump with record high efficiency of 10−4 [2]. This result paves the way to a wide range of applications requiring strong nonlinearities such as nonlinear microscopy, holography, and wave shaping [3]. However, so far, the physical origin of the strong nonlinear response in dielectric nanoparticles remains only partially understood. In this work, we investigate the emission properties of the SHG in individual monolithic AlGaAs-on-AlOx nanoantennas using polarization-resolved measurements. We found that the properties of the emitted SH depends strongly on the nanoantenna modes and that volume susceptibility has major role in the SHG process.
We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design ... more We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design nanoantennas with a magnetic dipole resonant mode in the near-infrared wavelength range, and we analyze volume second-harmonic generation driven by a magnetic dipole resonance by predicting a conversion efficiency exceeding 10-3 with 1 GW/cm2 of pump intensity.
In this work we propose a high-quality factor semiconductor nanoparticles array made of rectangul... more In this work we propose a high-quality factor semiconductor nanoparticles array made of rectangular silicon nanobricks. Our optimized metasurface can dramatically boost third harmonic generation, with a complex polarization dependence in the different diffraction orders.
Figure 1(b) in [V. F. Gili et al, Opt. Express 24, 15965 (2016)10.1364/OE.24.015965] is corrupted... more Figure 1(b) in [V. F. Gili et al, Opt. Express 24, 15965 (2016)10.1364/OE.24.015965] is corrupted and is corrected in this erratum.
We experimentally demonstrate the possibility to modulate the second harmonic (SH) power emitted ... more We experimentally demonstrate the possibility to modulate the second harmonic (SH) power emitted by nonlinear AlGaAs metasurfaces embedded in a liquid crystal (LC) matrix. This result is obtained by changing the relative in-plane orientation between the LC director and the linear polarization of the light at the excitation wavelength. According to numerical simulations, second-harmonic is efficiently radiated by the metasurfaces thanks to the sizeable second-order susceptibility of the material and the resonant excitation of either electric or magnetic dipole field distributions inside each meta-atom at the illuminating fundamental wavelength. This resonant behavior strongly depends on the geometric parameters, the crystallographic orientation, and the anisotropy of the metasurface, which can be optimized to modulate the emitted SH power by about one order of magnitude. The devised hybrid platforms are therefore appealing in view of enabling the electrical control of flat nonlinear optical devices.
Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light–m... more Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light–matter interaction based on multipolar resonances and plasmonics, hence offering the great capability of empowering nonlinear generation. Recently, owing to their ability to manipulate the amplitude and phase of the nonlinear emission in the subwavelength scale, metasurfaces have been recognized as ultra-compact, flat optical components for a vast range of applications, including nonlinear imaging, quantum light sources, and ultrasensitive sensing. This review focuses on the recent progress on nonlinear metasurfaces for those applications. The principles and advances of metasurfaces-based techniques for image generation, including image encoding, holography, and metalens, are investigated and presented. Additionally, the overview and development of spontaneous photon pair generation from metasurfaces are demonstrated and discussed, focusing on the aspects of photon pair generation rate an...
We develop a new approach based on quasi-BICs to develop chiral metasurfaces exhibiting nonlinear... more We develop a new approach based on quasi-BICs to develop chiral metasurfaces exhibiting nonlinear circular dichroism (up to 99.9%) and high conversion efficiency. Tuning mode interference allows selective linear and nonlinear circular dichroism.
A new branch of nonlinear nanophotonics based on high refractive index dielectric nanoparticles i... more A new branch of nonlinear nanophotonics based on high refractive index dielectric nanoparticles is emerging [1]. The unique large resonant enhancement of both electric and magnetic fields associated with very low dissipative losses considerably increases optical interactions at sub-wavelength scales opening new unexplored functionalities. Recently, AlGaAs nanodisks enabled second harmonic generation (SHG) from a near-infrared pump with record high efficiency of 10−4 [2]. This result paves the way to a wide range of applications requiring strong nonlinearities such as nonlinear microscopy, holography, and wave shaping [3]. However, so far, the physical origin of the strong nonlinear response in dielectric nanoparticles remains only partially understood. In this work, we investigate the emission properties of the SHG in individual monolithic AlGaAs-on-AlOx nanoantennas using polarization-resolved measurements. We found that the properties of the emitted SH depends strongly on the nanoantenna modes and that volume susceptibility has major role in the SHG process.
We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design ... more We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design nanoantennas with a magnetic dipole resonant mode in the near-infrared wavelength range, and we analyze volume second-harmonic generation driven by a magnetic dipole resonance by predicting a conversion efficiency exceeding 10-3 with 1 GW/cm2 of pump intensity.
In this work we propose a high-quality factor semiconductor nanoparticles array made of rectangul... more In this work we propose a high-quality factor semiconductor nanoparticles array made of rectangular silicon nanobricks. Our optimized metasurface can dramatically boost third harmonic generation, with a complex polarization dependence in the different diffraction orders.
Figure 1(b) in [V. F. Gili et al, Opt. Express 24, 15965 (2016)10.1364/OE.24.015965] is corrupted... more Figure 1(b) in [V. F. Gili et al, Opt. Express 24, 15965 (2016)10.1364/OE.24.015965] is corrupted and is corrected in this erratum.
We experimentally demonstrate the possibility to modulate the second harmonic (SH) power emitted ... more We experimentally demonstrate the possibility to modulate the second harmonic (SH) power emitted by nonlinear AlGaAs metasurfaces embedded in a liquid crystal (LC) matrix. This result is obtained by changing the relative in-plane orientation between the LC director and the linear polarization of the light at the excitation wavelength. According to numerical simulations, second-harmonic is efficiently radiated by the metasurfaces thanks to the sizeable second-order susceptibility of the material and the resonant excitation of either electric or magnetic dipole field distributions inside each meta-atom at the illuminating fundamental wavelength. This resonant behavior strongly depends on the geometric parameters, the crystallographic orientation, and the anisotropy of the metasurface, which can be optimized to modulate the emitted SH power by about one order of magnitude. The devised hybrid platforms are therefore appealing in view of enabling the electrical control of flat nonlinear optical devices.
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Papers by Davide Rocco