| 1. |
- Frigerio, Jacopo, et al.
(författare)
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Mid-infrared second harmonic generation in Ge/SiGe coupled quantum wells
- 2020
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Ingår i: 2020 IEEE Photonics Conference, IPC 2020 - Proceedings. ; September 2020
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Konferensbidrag (refereegranskat)abstract
- We present the theoretical investigation and the experimental demonstration of second harmonic generation in the mid-infrared by hole-doped Ge/SiGe asymmetric quantum wells.
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| 2. |
- Frigerio, Jacopo, et al.
(författare)
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Mid-infrared second harmonic generation with Ge quantum wells
- 2021
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Ingår i: IEEE International Conference on Group IV Photonics GFP. - 1949-2081. ; 2021-December
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Konferensbidrag (refereegranskat)abstract
- We present the experimental demonstration of second harmonic generation in the mid-infrared by hole-doped Ge/SiGe asymmetric quantum wells.
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| 3. |
- Frigerio, Jacopo, et al.
(författare)
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Second Harmonic Generation in Germanium Quantum Wells for Nonlinear Silicon Photonics
- 2021
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 8:12, s. 3573-3582
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Tidskriftsartikel (refereegranskat)abstract
- Second-harmonic generation (SHG) is a direct measure of the strength of second-order nonlinear optical effects, which also include frequency mixing and parametric oscillations. Natural and artificial materials with broken center-of-inversion symmetry in their unit cell display high SHG efficiency, however, the silicon-foundry compatible group IV semiconductors (Si, Ge) are centrosymmetric, thereby preventing full integration of second-order nonlinearity in silicon photonics platforms. Here we demonstrate strong SHG in Ge-rich quantum wells grown on Si wafers. Unlike Si-rich epilayers, Ge-rich epilayers allow for waveguiding on a Si substrate. The symmetry breaking is artificially realized with a pair of asymmetric coupled quantum wells (ACQW), in which three of the quantum-confined states are equidistant in energy, resulting in a double resonance for SHG. Laser spectroscopy experiments demonstrate a giant second-order nonlinearity at mid-infrared pump wavelengths between 9 and 12 μm. Leveraging on the strong intersubband dipoles, the nonlinear susceptibility χ(2) almost reaches 105 pm/V, 4 orders of magnitude larger than bulk nonlinear materials for which, by the Miller's rule, the range of 10 pm/V is the norm.
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| 4. |
- Koya, Alemayehu Nana, et al.
(författare)
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Control of particle trapping in solid-state nanopores with magnetic functionalities : An overview
- 2022
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. - 9781510651388 - 9781510651395
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Konferensbidrag (refereegranskat)abstract
- In the last decade, solid-state nanopores have been intensively investigated as label-free detectors of for single biological entities, such as protein chains or DNA molecules. With this approach, single entities are typically driven through a nanopore by applying an external electrical potential. However, this method cannot enable control over the speed of translocation, thus limiting the signal integration time. The most explored approach to introduce control of the translocation speed is based on trapping. In particular, a long acquisition time can be obtained by trapping a nanoparticle tagged with molecules close to a nanopore. The trapping phenomena can be generated by means of external stimuli such as light excitation and magnetic field application, obtaining respectively the so-called optical and magnetic trapping. Magnetic trapping, in particular, has been less explored but can be a useful approach to obtain very large trapping forces without interfering with other optical exitations that can be used for spectroscopic purposes. Here, we will briefly summarize the major examples of magnetic trapping approaches reported so far in solid-state nanopore technology.
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| 5. |
- Kuttruff, Joel, et al.
(författare)
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Broadband tuning of the magneto-optical response of hybrid metal-insulator nanoparticles enabled by hyperbolic electric and magnetic modes
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the framework of magneto-photonics, the optical properties of a material can controlled by an external magnetic field, providing active functionalities for applications, such as sensing and nonreciprocal optical isolation. For noble metals in particular, the inherently weak magnetooptical coupling of the bulk material can be greatly enhanced via excitation of localized surface plasmons (LSP) in nanostructured samples. Hyperbolic metamaterials therein provide the ideal platform to tune the plasmonic properties via careful design of the effective permittivity tensor. Here, we report on the magnetic circular dichroism of electric and magnetic dipole modes of a type II hyperbolic metasurface. Disk-shaped nanoparticles consist in stacks of alternating dielectric and metallic layers. Using an effective medium theory, we show that the optical properties of the system can be perfectly described by an anisotropic homogenized permittivity. Magnetic circular dichroism spectroscopy experiments are compared with plain gold disk samples and reveal a broadband magneto-optical response across the visible and near infrared spectral range. In particular, derivative-like spectral signatures at the resonances of the nanoparticles prove the induced dichroism for the two modes of the system. Results are interpreted in terms of magnetically induced spatial confinement/broadening of circular currents in the nanoparticles and are compared with a comprehensive numerical model based on the finite elements method using the real dimensions of the nanostructure. Spherical particles are employed as an analytical model system, allowing to generalize the contribution of electric and magnetic modes to the total magneto-optical response. More in detail, interaction cross sections are calculated as a weighted sum of the corresponding Mie coefficients. Utilizing a perturbative approach, we describe the magneto-optical effect in terms of linear changes in the cyclotron frequency of free charge carriers in the metal. By comparing our analytical model with full-wave numerical results, we can identify the contribution of electric and magnetic dipole modes to the spectrum and reproduce the spectral line shape we observe in the experiments for the hyperbolic nanoparticles.
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| 6. |
- Kuttruff, Joel, et al.
(författare)
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Magneto-Optical Activity in Nonmagnetic Hyperbolic Nanoparticles
- 2021
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity in nonmagnetic hyperbolic nanoparticles. We demonstrate that the magneto-optical response is driven by the hyperbolic dispersion via the coupling of metallic-induced electric and dielectric-induced magnetic dipolar optical modes with static magnetic fields. Magnetic circular dichroism experiments confirm the theoretical predictions and reveal tunable magneto-optical activity across the visible and near infrared spectral range.
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| 7. |
- Kuttruff, Joel, et al.
(författare)
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Magneto-Optical Activity in Nonmagnetic Hyperbolic Nanoparticles
- 2021
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 127:21
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Tidskriftsartikel (refereegranskat)abstract
- Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity in nonmagnetic hyperbolic nanoparticles. We demonstrate that the magneto-optical response is driven by the hyperbolic dispersion via the coupling of metallic-induced electric and dielectric-induced magnetic dipolar optical modes with static magnetic fields. Magnetic circular dichroism experiments confirm the theoretical predictions and reveal tunable magneto-optical activity across the visible and near infrared spectral range.
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| 8. |
- Kuttruff, Joel, et al.
(författare)
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Magneto-optics in hyperbolic nanomaterials
- 2021
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Konferensbidrag (refereegranskat)abstract
- Hyperbolic nanoparticles provide a versatile platform to widely tune light-matter interactions. Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical response of hyperbolic nanoparticles across the visible and near infrared spectral range. By using a perturbative approach, we establish a model where the magneto-optical activity of the system is described in terms of the coupling of fundamental electric and magnetic dipole modes, which are induced by the hyperbolic dispersion, with a static magnetic field. Finally, an analytical model is established in the framework of Mie theory to describe the magneto-optical response and identify the contribution of electric and magnetic modes to the total spectrum.
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| 9. |
- Kuttruff, Joel, et al.
(författare)
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Sub-picosecond collapse of molecular polaritons to pure molecular transition in plasmonic photoswitch-nanoantennas
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723 .- 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Molecular polaritons are hybrid light-matter states that emerge when a molecular transition strongly interacts with photons in a resonator. At optical frequencies, this interaction unlocks a way to explore and control new chemical phenomena at the nanoscale. Achieving such control at ultrafast timescales, however, is an outstanding challenge, as it requires a deep understanding of the dynamics of the collectively coupled molecular excitation and the light modes. Here, we investigate the dynamics of collective polariton states, realized by coupling molecular photoswitches to optically anisotropic plasmonic nanoantennas. Pump-probe experiments reveal an ultrafast collapse of polaritons to pure molecular transition triggered by femtosecond-pulse excitation at room temperature. Through a synergistic combination of experiments and quantum mechanical modelling, we show that the response of the system is governed by intramolecular dynamics, occurring one order of magnitude faster with respect to the uncoupled excited molecule relaxation to the ground state.
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| 10. |
- Kuttruff, Joel, et al.
(författare)
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Ultrafast all-optical switching enabled by epsilon-near-zero-tailored absorption in metal-insulator nanocavities
- 2020
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Ingår i: Communications Physics. - : Nature Publishing Group. - 2399-3650. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature switching speeds that are extremely low with respect to the time scales at which it is possible to control light. Here, we exploit the artificial epsilon-near-zero (ENZ) modes of a metal-insulator-metal nanocavity to tailor the linear photon absorption of our system and realize a nondegenerate all-optical ultrafast modulation of the reflectance at a specific wavelength. Optical pumping of the system at its high energy ENZ mode leads to a strong redshift of the low energy mode because of the transient increase of the local dielectric function, which leads to a sub-3-ps control of the reflectance at a specific wavelength with a relative modulation depth approaching 120%.
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