All‐Optical Modulation with Dielectric Nanoantennas: Multiresonant Control and Ultrafast Spatial Inhomogeneities

Mazzanti, Andrea; Pogna, Eva A. A.; Ghirardini, Lavinia; Celebrano, Michele; Schirato, Andrea; Marino, Giuseppe; Lemaı̂tre, A.; Finazzi, Marco; Angelis, Costantino De; Leo, Giuseppe; Cerullo, Giulio; Valle, Giuseppe Della

doi:10.1002/smsc.202000079

Cited by 11 publications

(7 citation statements)

References 41 publications

(57 reference statements)

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“…Upon a change of the NP constituent medium permittivity Δε , the optical transmittance evolves from T (ε) to T (ε + Δε ) . When Δε ≪ ε, a perturbative approach can be applied to determine ΔT = T (ε + Δε ) – T (ε) = ∂ T /∂ε × Δε (see, e.g., refs − ). Yet, generally the evolution from T (ε) to T (ε + Δε ) is not perturbative, and ΔT does not scale linearly with Δε , as depicted in Figure a.…”

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confidence: 99%

Ultrafast Plasmonics Beyond the Perturbative Regime: Breaking the Electronic-Optical Dynamics Correspondence

et al. 2022

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The transient optical response of plasmonic nanostructures has recently been the focus of extensive research. Accurate prediction of the ultrafast dynamics following excitation of hot electrons by ultrashort laser pulses is of major relevance in a variety of contexts from the study of light harvesting and photocatalytic processes to nonlinear nanophotonics and the all-optical modulation of light. So far, all studies have assumed the correspondence between the temporal evolution of the dynamic optical signal, retrieved by transient absorption spectroscopy, and that of the photoexcited hot electrons, described in terms of their temperature. Here, we show both theoretically and experimentally that this correspondence does not hold under a nonperturbative excitation regime. Our results indicate that the main mechanism responsible for the breaking of the correspondence between electronic and optical dynamics is universal in plasmonics, being dominated by the nonlinear smearing of the Fermi–Dirac occupation probability at high hot-electron temperatures.

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confidence: 99%

Ultrafast Plasmonics Beyond the Perturbative Regime: Breaking the Electronic-Optical Dynamics Correspondence

et al. 2022

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“…For the AlGaAs, the carrier density is evaluated by Keldysh photoionization rate normal∂Nenormal∂t=wPIfalse(∣Efalse→∣,normalλ,Eg,me∗false)−Ne/normalτrec for the electric field Efalse→ and laser wavelength λ, whereas constant E g = 1.67 eV, me∗=0.07.1emme, τ rec = 11 ps, and ν e ~10 13 s −1 are adopted from ( 35 ) in the ionization model. In the absence of carriers, the third-order Kerr-like response is given by polarization P(3)→=normalε0normalχfalse(3false)false(Efalse→Efalse→false)Efalse→ with χ (3) = 3.4 · 10 −19 m 2 /V 2 ( 36 ) and the second-order response for noncentrosymmetric material by P(2)→=normalε0normalχfalse(2false)false(EyEz,ExEz,ExEyfalse) ( 37 ) with χ (2) ~300 pm/V ( 38 ).…”

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confidence: 99%

High-harmonic generation from a subwavelength dielectric resonator

et al. 2023

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Higher-order optical harmonics entered the realm of nanostructured solids being observed recently in optical gratings and metasurfaces with a subwavelength thickness. Structuring materials at the subwavelength scale allows us toresonantly enhance the efficiency of nonlinear processes and reduce the size of high-harmonic sources. We report the observation of up to a seventh harmonic generated from a single subwavelength resonator made of AlGaAs material. This process is enabled by careful engineering of the resonator geometry for supporting an optical mode associated with a quasi-bound state in the continuum in the mid-infrared spectral range at around λ = 3.7 μm pump wavelength. The resonator volume measures ~0.1 λ 3 . The resonant modes are excited with an azimuthally polarized tightly focused beam. We evaluate the contributions of perturbative and nonperturbative nonlinearities to the harmonic generation process. Our work proves the possibility to miniaturize solid-state sources of high harmonics to the subwavelength volumes.

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“…Besides the difference in amplitude, the rise time of the modulated signal in the case of an inhomogeneous approach is almost doubled (from ∼400 fs to ∼800 fs). Such delay effect in reaching the peak is indeed assigned to spatio-temporal inhomogeneities taking place at the nanoscale [55] and explained as the fingerprint of a homogenization process undergone by excitation across the individual meta-atoms, which modifies the dynamics of the optical excitation. However, the most striking difference between model predictions is observed at λ 1 = 610 nm (top curves in figure 4(d)).…”

Section: Tapered Cross Section Nanowire Metasurfacementioning

confidence: 95%

Hot carrier spatio-temporal inhomogeneities in ultrafast nanophotonics

et al. 2022

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Light-induced hot carriers in nanostructures and their corresponding optical nonlinearity have been extensively examined during the last decades. However, nonlinear optical effects dictated by the spatio-temporal evolution of out-of-equilibrium electrons at the nanoscale represent a much more recent research focus. Here we theoretically discuss the role of spatial inhomogeneities that energetic electrons feature across individual nanoantennas in metasurface configuration upon illumination with femtosecond laser pulses. As exemplary cases, we consider two-dimensional geometries of gold meta-atoms having either a high aspect ratio or a tapered cross-section and model their ultrafast optical response. A comparison with numerical results obtained either neglecting or accounting for spatial effects indicates that deep sub-wavelength spatio-temporal transients of carriers may have a significant impact on the dynamics of the all- optically modulated signal, with major quantitative corrections up to predicted changes in sign. Our results present hot-electron local inhomogeneities as an emerging subject with potentially relevant applications in various ultrafast nanophotonic configurations.

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All‐Optical Modulation with Dielectric Nanoantennas: Multiresonant Control and Ultrafast Spatial Inhomogeneities

Cited by 11 publications

References 41 publications

Ultrafast Plasmonics Beyond the Perturbative Regime: Breaking the Electronic-Optical Dynamics Correspondence

Ultrafast Plasmonics Beyond the Perturbative Regime: Breaking the Electronic-Optical Dynamics Correspondence

High-harmonic generation from a subwavelength dielectric resonator

Hot carrier spatio-temporal inhomogeneities in ultrafast nanophotonics

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