| 1. |
- Mante, Pierre Adrien, et al.
(författare)
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Confinement effects on Brillouin scattering in semiconductor nanowire photonic crystal
- 2016
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Ingår i: Physical Review B. - 1098-0121. ; 94:2
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Tidskriftsartikel (refereegranskat)abstract
- Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control of light and has led to revolutionary applications, from slow light to saser and cooling of micromechanical resonators. Recently, enhanced light and sound interaction has been demonstrated in waveguides. However, the design of the waveguide geometry tunes and alters the phonon and photon dispersion simultaneously. Here we investigate, through femtosecond pump-probe spectroscopy and theoretical modeling, the light and sound interaction in a bottom-up fabricated vertical nanowire photonic crystal. In such a system, the phonon dispersion can be tuned by varying the geometry of the constituent nanowires. In contrast, the placement of the nanowires in the photonic crystal can be used for tuning optical array modes, without altering the phonon dispersion. We demonstrate the forward and backward scattering, by acoustic phonons in the nanowires, of (1) such optical array modes and (2) guided modes of the constituent nanowires. Furthermore, our results reveal an enhanced interaction of array modes with phonons that we attribute to the specific scattering mechanism. Our results enable the design of a photonic crystal with separately tailored photon and phonon dispersion for Brillouin scattering. We anticipate these advances to be a starting point for enhanced control of light at the nanoscale.
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| 2. |
- Berg, Alexander, et al.
(författare)
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Growth and characterization of wurtzite GaP nanowires with control over axial and radial growth by use of HCl in-situ etching
- 2014
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 386, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of non-tapered wurtzite (WZ) GaP nanowires by use of in-situ etching and the structural and optical characterization thereof. HCl was evaluated as an in-situ etchant in order to impede the onset of radial growth since the WZ crystal phase in GaP nanowires preferentially grows at relatively high growth temperatures around 600 degrees C, at which strong radial growth typically occurs. Transmission electron microscopy measurements confirmed non-tapered WZ GaP nanowires after growth. Photoluminescence characterization revealed defect related red emission, possibly related to transitions within the bandgap. Raman measurements show that the phonon energies in WZ GaP are very close in energy to the phonon energies in zinc blende GaP. (C) 2013 Elsevier B.V. All rights reserved.
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| 3. |
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| 4. |
- Lehmann, Sebastian, et al.
(författare)
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Simultaneous Growth of Pure Wurtzite and Zinc Blende Nanowires
- 2019
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:4, s. 2723-2730
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Tidskriftsartikel (refereegranskat)abstract
- The opportunity to engineer III-V nanowires in wurtzite and zinc blende crystal structure allows for exploring properties not conventionally available in the bulk form as well as opening the opportunity for use of additional degrees of freedom in device fabrication. However, the fundamental understanding of the nature of polytypism in III-V nanowire growth is still lacking key ingredients to be able to connect the results of modeling and experiments. Here we show InP nanowires of both pure wurtzite and pure zinc blende grown simultaneously on the same InP [100]-oriented substrate. We find wurtzite nanowires to grow along «111»B and zinc blende counterparts along «111»A. Further, we discuss the nucleation, growth, and polytypism of our nanowires against the background of existing theory. Our results demonstrate, first, that the crystal growth conditions for wurtzite and zinc blende nanowire growth are not mutually exclusive and, second, that the interface energies predominantly determine the crystal structure of the nanowires.
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| 5. |
- Mante, Pierre-Adrien, et al.
(författare)
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Ultrafast Optical Generation of Coherent Bright and Dark Surface Phonon Polaritons in Nanowires
- 2020
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:8, s. 1923-1931
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Tidskriftsartikel (refereegranskat)abstract
- The subwavelength confinement and enhanced electric field created by plasmons allow precise sensing and enhanced light–matter interaction. However, the high frequency and short lifetime of plasmons limit the full potential of this technology. It is crucial to find substitutes and to study their dynamics. Here, we propose an experimental approach allowing the time-domain study of surface phonon polaritons. We first build a theoretical framework for the interaction of ultrashort pulses of light with polar materials. We then perform femtosecond pump–probe experiments and demonstrate the generation and time-resolved detection of surface phonon polaritons. By comparing experiments and simulations, we show the presence of both bright and dark modes with quality factors up to 115. We then investigate mode-dependent decay and energy transfer to the environment. Our results offer a platform for the experimental exploration of the dynamics of surface phonon polaritons and of the role of coherence in energy transfer.
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| 6. |
- Mergenthaler, Kilian, et al.
(författare)
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Large-energy-shift photon upconversion in degenerately doped InP nanowires by direct excitation into the electron gas
- 2013
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 6:10, s. 752-757
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Tidskriftsartikel (refereegranskat)abstract
- Realizing photon upconversion in nanostructures is important for many next-generation applications such as biological labelling, infrared detectors and solar cells. In particular nanowires are attractive for optoelectronics because they can easily be electrically contacted. Here we demonstrate photon upconversion with a large energy shift in highly n-doped InP nanowires. Crucially, the mechanism responsible for the upconversion in our system does not rely on multi-photon absorption via intermediate states, thus eliminating the need for high photon fluxes to achieve upconversion. The demonstrated upconversion paves the way for utilizing nanowires-with their inherent flexibility such as electrical contactability and the ability to position individual nanowires-for photon upconversion devices also at low photon fluxes, possibly down to the single photon level in optimised structures.
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| 7. |
- Mergenthaler, Kilian, et al.
(författare)
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Photon upconversion in degenerately sulfur doped InP nanowires.
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:48, s. 20503-20509
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Tidskriftsartikel (refereegranskat)abstract
- Radiative recombination in degenerately n-doped InP nanowires is studied for excitation above and below the Fermi energy of the electron gas, using photoluminescence. Laser-induced electron heating is observed, which allows absorption below the Fermi energy. We observe photon upconversion where photo-excited holes recombine with high |k| electrons. This can be attributed to hole scattering to high |k|-values, and the temperature dependence of this process is measured. We show that hole relaxation via phonon scattering can be observed in continuous wave excitation luminescence measurements.
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| 8. |
- Zhang, Wei, et al.
(författare)
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Carrier Recombination Dynamics in Sulfur-Doped InP Nanowires.
- 2015
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:11, s. 7238-7244
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Tidskriftsartikel (refereegranskat)abstract
- Measuring lifetime of photogenerated charges in semiconductor nanowires (NW) is important for understanding light-induced processes in these materials and is relevant for their photovoltaic and photodetector applications. In this paper, we investigate the dynamics of photogenerated charge carriers in a series of as-grown InP NW with different levels of sulfur (S) doping. We observe that photoluminescence (PL) decay time as well as integrated PL intensity decreases with increasing S doping. We attribute these observations to hole trapping with the trap density increased due to S-doping level followed by nonradiative recombination of trapped charges. This assignment is proven by observation of the trap saturation in three independent experiments: via excitation power and repetition rate PL lifetime dependencies and by PL pump-probe experiment.
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