Degenerate optical nonlinear enhancement in epsilon-near-zero transparent conducting oxides

Carnemolla, Enrico Giuseppe; Caspani, Lucia; DeVault, Clayton; Clerici, Matteo; Vezzoli, Stefano; Bruno, Vincenzo; Shalaev, Vladimir M.; Faccio, Daniele; Boltasseva, Alexandra; Ferrera, Marcello

doi:10.1364/ome.8.003392

Cited by 56 publications

(54 citation statements)

References 35 publications

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“…Following the recent works in TCOs, this can be explained by the fact that the dielectric permittivity, and so the optical constants including λ ENZ , exhibit a redshift when it is optically pumped across the ENZ wavelength [31,44]. The redshift of the λ ENZ is also associated to a positive ∆n and to a negative ∆k [30,32]. Due to the decreasing of k, the visibility drops, as we observed for the linear case.…”

Section: Coherent Absorption and Its Dynamical Controlsupporting

confidence: 65%

“…We theoretically and experimentally explore the role of this transition region in order to achieve CPA in homogeneous AZO optically thick films and then show how this can be controlled with intense optical pump fields. It was recently shown that the combination of low refractive index and the high damage threshold of these materials allows TCOs to exhibit large and ultrafast Kerr-type optical nonlinearities in the ENZ region [30][31][32][33][34][35][36] and behave as efficient time-varying medium [37,38].…”

Section: Introductionmentioning

confidence: 99%

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Dynamical Control of Broadband Coherent Absorption in ENZ Films

et al. 2020

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Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of the scattering matrix and often requires engineered optical properties. For instance, thin film CPA benefits from complex nanostructures with suitable resonance, albeit at a loss of operational bandwidth. In this work, we theoretically and experimentally demonstrate a broadband CPA based on light-with-light modulation in epsilon-near-zero (ENZ) subwavelength films. We show that unpatterned ENZ films with different thicknesses exhibit broadband CPA with a near-unity maximum value located at the ENZ wavelength. By using Kerr optical nonlinearities, we dynamically tune the visibility and peak wavelength of the total energy modulation. Our results based on homogeneous thick ENZ media open a route towards on-chip devices that require efficient light absorption and dynamical tunability.

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Section: Coherent Absorption and Its Dynamical Controlsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Dynamical Control of Broadband Coherent Absorption in ENZ Films

et al. 2020

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“…is shorter near the ENZ condition due to the slow propagation velocity. This represents a significant advantage, giving rise to three benefits: 1) the potential to use thinner materials, 2) an improved temporal overlap of the light with slower and therefore stronger nonlinearities (as was employed in [7,8]), and 3) a reduction in the pump intensity for a given δε , because respectively. It is important to note that this enhancement is not intrinsic to ENZ materials as it is entirely due to slow propagation.…”

Section: Real Benefit Of Enz Materialsmentioning

confidence: 99%

Adiabatic frequency shifting in epsilon-near-zero materials: the role of group velocity

Khurgin¹,

Clerici²,

Bruno³

et al. 2020

Optica

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We investigate adiabatic frequency conversion using epsilon near zero (ENZ) materials. We show that, while the maximum frequency conversion for a given change of permittivity does not exhibit an increase in the vicinity of the Re[εr]=0 condition, the change in permittivity can be achieved in a shorter length and, if the pump is also in the ENZ region, at a lower pump intensity. This slow propagation effect makes the conversion efficiency in the ENZ material comparable to that in micro-resonators and other structured slow light schemes, but unlike the latter, no nanofabrication is required for ENZ materials which constitutes their major advantage over alternative frequency conversion approaches. Our results, supported by experimental measurements, indicate that transparent metal oxides operating near the ENZ point are good candidates for future frequency conversion schemes. INTRODUCTIONFrequency conversion is a signature characteristic and a key application of nonlinear optics [1]. It can be attained using both second and third order nonlinearities in various media. Second order processes require noncentrosymmetric media and include the well-known effects of sum and difference frequency generation while third order phenomena, which occur in any medium, include four-wave mixing processes as well as Raman effects. All of these frequency conversion schemes can be characterized as parametric processes where the optical properties are modulated with a certain frequency which causes the generation of oscillations at new frequencies. Typically, frequency conversion is well described by the coupled wave formalism [2] in which the energy flows back and forth between waves of different frequencies (often characterized as pump, signal and idler) depending on the phase relations between the waves (phase matching conditions).While the field of frequency conversion is well established, the development of powerful ultra-fast light sources has led to the observation of different effects where the entire spectrum of the incoming light wave shifts adiabatically in the presence of a rapid change of the refractive index, typically induced by a strong optical pump (although other methods are possible). These effects have been observed both in high-Q resonant dielectric structures (Fig. 1a) [3][4][5][6] and in free propagating waves inside nonlinear epsilon-near zero (ENZ) media [7][8][9]. Although several nonlinear processes have been shown to be enhanced in ENZ materials (Fig. 1b) [10][11][12], driving intense research [13,14], rapid and complete frequency conversion/ modulation represents a unique opportunity to explore novel applications, especially in imaging, sensing, and telecommunications. Currently, the research on adiabatic frequency conversion (AFC) is ongoing and it is not clear which approach (i.e. high-Q resonators or ENZ) is the most appropriate. With that in mind, we explore what characteristics are needed to achieve efficient AFC, giving special attention to ENZ materials, were we find the potential for large frequency...

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“…Transparent conductive oxide thin films display enhanced nonlinear optical properties at epsilon-near-zero region [7][8][9]. It is of importance to investigate the optical nonlinearity of the Mie resonant metasurface at the transition of effective refractive index through zero value.…”

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confidence: 99%

“…The similar maximum of n 2 was observed in Refs. [8,9] for Al-doped ZnO thin films which possess epsilon-nearzero conditions at infrared wavelengths. The authors of Refs.…”

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confidence: 99%

Optical Kerr Nonlinearity of Disordered All-Dielectric Resonant High Index Metasurfaces with Negative Refraction

Panov

2020

Jetp Lett.

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The optical Kerr effect of material with negative refraction is estimated for the first time. This is done via three-dimensional finite-difference time-domain (FDTD) simulations of disordered bidisperse metasurfaces consisting of high index (GaP) spheres at the wavelength of 532 nm. The metasurfaces comprise spherical particles randomly arranged on plane having two sizes close to the magnetic and electric dipole Mie resonances. The real part of the effective nonlinear refractive index of the metasurfaces is computed in the vicinity of the Mie resonances where the metasurface possesses the negative index of refraction. The optical Kerr nonlinearity has a peak under the condition for the negative refraction. Intensity-dependent refractive index of the bidisperse metasurfaces is studied through concentration transition to the negative refraction state. It is shown that the nonlinear Kerr coefficient of the monolayer metasurface has maximum when the effective linear refractive index is close to zero.

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Degenerate optical nonlinear enhancement in epsilon-near-zero transparent conducting oxides

Cited by 56 publications

References 35 publications

Dynamical Control of Broadband Coherent Absorption in ENZ Films

Dynamical Control of Broadband Coherent Absorption in ENZ Films

Adiabatic frequency shifting in epsilon-near-zero materials: the role of group velocity

Optical Kerr Nonlinearity of Disordered All-Dielectric Resonant High Index Metasurfaces with Negative Refraction

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