0000000000918207
AUTHOR
Giuseppe Leo
Second Harmonic Emission From Dielectric Nanoresonators in the Absorption Regime
We study second harmonic generation in dielectric nanocylinders as a function of the wavelength of the incident field and geometrical dimensions. Uncommonly, we consider a spectral range in which the emitted nonlinear signal is partially absorbed by the dielectric. Surprisingly, we reveal that the second harmonic efficiency does not decrease as the imaginary part of the complex dielectric refractive index increases. Indeed, the presence of higher order multipoles supported by the resonators at the fundamental wavelength can significantly boost the generated second harmonic signal even in the dielectric absorption spectral region achieving nonlinear efficiency of the same order of magnitude …
Second harmonic generation in coupled LiNbO3 waveguides by reverse-proton exchange
We demonstrate second harmonic generation of a near-infrared pump in a nonlinearly coupled system formed by longitudinally uniform proton- and reverse-proton-exchanged LiNbO/sub 3/ planar waveguides. Phase- and mode-matched transverse electric (TE/sub 0/) frequency doubling into transverse magnetic higher order guided modes is achieved through temperature control, in agreement with the model.
Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces
We demonstrate optically tunable control of second-harmonic generation in all-dielectric nanoantennas: by using a control beam that is absorbed by the nanoresonator, we thermo-optically change the refractive index of the radiating element to modulate the amplitude of the second-harmonic signal. For a moderate temperature increase of roughly 40 K, modulation of the efficiency up to 60% is demonstrated; this large tunability of the single meta-atom response paves the way to exciting avenues for reconfigurable homogeneous and heterogeneous metasurfaces.
Bi-color spatial solitons in linearly uncoupled planar waveguides
We report on the observation of spatial optical simultons in a novel geometry consisting of two partially overlapped, linearly uncoupled planar waveguides in lithium niobate obtained by reverse proton exchange. Two orthogonally polarized modes are coupled through an off-diagonal tensor element of the quadratic nonlinearity, giving rise to second harmonic generation and mutual trapping via cascading. This phenomenon demonstrates a balance between diffraction and self-focusing for two orthogonal modes of different waveguides, and occurs at room temperature in longitudinally uniform waveguides.
Second order nonlinear optics in AlGaAs metasurfaces
Recently, nonlinear optics at the nanoscale level has emerged as a promising branch of nanophotonics. In this work, we focus our attention on Aluminum Gallium Arsenide (AlGaAs) nanoantennas and metasurfaces for efficient and controlled second harmonic photon emission. After a brief introduction concerning the main studies in this field, we present the latest results achieved in AlGaAs platforms both in the lossless and absorption regimes.
Opto-thermally controlled beam steering in nonlinear all-dielectric metastructures
Reconfigurable metasurfaces have recently gained a lot of attention in applications such as adaptive meta-lenses, hyperspectral imaging and optical modulation. This kind of metastructure can be obtained by an external control signal, enabling us to dynamically manipulate the electromagnetic radiation. Here, we theoretically propose an AlGaAs device to control the second harmonic generation (SHG) emission at nanoscale upon optimized optical heating. The asymmetric shape of the used meta-atom is selected to guarantee a predominant second harmonic (SH) emission towards the normal direction. The proposed structure is concurrently excited by a pump beam at a fundamental wavelength of 1540 nm and…