| 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. |
- Keller, Kilian R., et al.
(författare)
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Ultrafast control of exciton dynamics by optically-induced thermionic carrier injection in a metal-semiconductor heterojunction
- 2023
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Ingår i: Smart materials for opto-electronic applications. - Washington : SPIE - The International Society for Optics and Photonics. - 9781510662889 - 9781510662896
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Konferensbidrag (refereegranskat)abstract
- Interface effects in metals-semiconductors heterojunctions are subject of intense research due to the possibility to exploit the synergy between their electronic and optical properties in next-generation opto-electronic devices. In this framework, understanding the carrier dynamics at the metal-semiconductor interface, as well as achieving a coherent control of charge and energy transfer in metal-semiconductor heterostructures, are crucial and yet quite unexplored aspects. Here, we experimentally show that thermionically injected carriers from a gold substrate can drastically affect the dynamics of excited carriers in bulk WS2. By employing a pump-push-probe scheme, where a push pulse excites direct transitions in the WS2, and another delayed pump pulse induces thermionic injection of carriers from the gold substrate into the semiconductor, we can control both the formation and annihilation of excitons. Our findings might foster the development of novel opto-electronic approaches to control charge dynamics using light at ultrafast timescales.
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| 5. |
- Keller, Kilian R., et al.
(författare)
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Ultrafast Thermionic Electron Injection Effects on Exciton Formation Dynamics at a van der Waals Semiconductor/Metal Interface
- 2022
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 9:8, s. 2683-2690
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic van der Waals bonded semiconductors such as transition metal dichalcogenides are the subject of intense research due to their electronic and optical properties which are promising for next-generation optoelectronic devices. In this context, understanding the carrier dynamics, as well as charge and energy transfer at the interface between metallic contacts and semiconductors, is crucial and yet quite unexplored. Here, we present an experimental study to measure the effect of mutual interaction between thermionically injected and directly excited carriers on the exciton formation dynamics in bulk WS2. By employing a pump–push–probe scheme, where a pump pulse induces thermionic injection of electrons from a gold substrate into the conduction band of the semiconductor, and another delayed push pulse that excites direct transitions in the WS2, we can isolate the two processes experimentally and thus correlate the mutual interaction with its effect on the ultrafast dynamics in WS2. The fast decay time constants extracted from the experiments show a decrease with an increasing ratio between the injected and directly excited charge carriers, thus disclosing the impact of thermionic electron injection on the exciton formation dynamics. Our findings might offer a new vibrant direction for the integration of photonics and electronics, especially in active and photodetection devices, and, more in general, in upcoming all-optical nanotechnologies.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- Kuttruff, Joel, et al.
(författare)
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Ultrafast Dynamics of Molecular Polaritons in Photoswitch Nanoantennas
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350345995
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Konferensbidrag (refereegranskat)abstract
- We study ultrafast dynamics of photocromic molecules both weakly and strongly coupled to plasmonic nanoantennas. Experiments, verified by quantum modelling, reveal subps collapse of molecular polaritons to intramolecular dynamics induced by interaction with the plasmons.
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| 9. |
- Kuttruff, Joel, et al.
(författare)
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Ultrafast Dynamics of Photochromic Molecules Coupled to Anisotropic Plasmon Nanoantennas
- 2022
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Ingår i: CLEO: 2022. - Washington, D.C. : Optica Publishing Group. - 9781957171050
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Konferensbidrag (refereegranskat)abstract
- We study coupling of merocyanine to aluminum nanoantennas in weak and strong interaction regimes. Experiments reveal modification of the molecular dynamics induced by the plasmons as verified by quantum modelling of the hybrid system.
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| 10. |
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