| 1. |
- Arnold, Cord L., et al.
(author)
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A high-repetition rate attosecond pulse source for coincidence spectroscopy
- 2021
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In: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781665418768
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Conference paper (peer-reviewed)abstract
- The power of attosecond pump-probe spectroscopy combined with advanced detection schemes, such as photoelectron/ion coincidence spectrometers and time-resolved photoelectron emission microscopy (PEEM), can be unleashed by properly accounting for the repetition rate of the source. In this work, we present a high-repetition rate (200 kHz) attosecond pulse source that opens up for exploring phenomena, previously inaccessible to the community using attosecond interferometric and spectroscopy pump-probe techniques [1].
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| 2. |
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| 3. |
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| 4. |
- Balla, Prannay, et al.
(author)
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Post-compression of picosecond pulses to four optical cycles
- 2020
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In: High Intensity Lasers and High Field Phenomena, HILAS 2020. - 9781557528209
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Conference paper (peer-reviewed)abstract
- We report post-compression of 1.2 ps pulses into the few-cycle regime via multi-pass spectral broadening. We achieve compression factors of 40 in single and 93 in a dual stage scheme using a compact setup.
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| 5. |
- Balla, Prannay, et al.
(author)
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Postcompression of picosecond pulses into the few-cycle regime
- 2020
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In: Optics Letters. - 0146-9592. ; 45:9, s. 2572-2575
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Journal article (peer-reviewed)abstract
- In this work,we demonstrate postcompression of 1.2 ps laser pulses to 13 fs via gas-based multipass spectral broadening. Our results yield a single-stage compression factor of about 40 at 200 W in-burst average power and a total compression factor >90 at reduced power. The employed scheme represents a route toward compact few-cycle sources driven by industrial-grade Yb:YAG lasers at high average power.
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| 6. |
- Cheng, Yu Chen, et al.
(author)
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Controlling photoionization using attosecond time-slit interferences
- 2020
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 117:20, s. 10727-10732
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Journal article (peer-reviewed)abstract
- When small quantum systems, atoms or molecules, absorb a high-energy photon, electrons are emitted with a well-defined energy and a highly symmetric angular distribution, ruled by energy quantization and parity conservation. These rules are based on approximations and symmetries which may break down when atoms are exposed to ultrashort and intense optical pulses. This raises the question of their universality for the simplest case of the photoelectric effect. Here we investigate photoionization of helium by a sequence of attosecond pulses in the presence of a weak infrared laser field. We continuously control the energy of the photoelectrons and introduce an asymmetry in their emission direction, at variance with the idealized rules mentioned above. This control, made possible by the extreme temporal confinement of the light-matter interaction, opens a road in attosecond science, namely, the manipulation of ultrafast processes with a tailored sequence of attosecond pulses.
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| 7. |
- Guo, Chen, et al.
(author)
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Compact 200 kHz HHG source driven by a few-cycle OPCPA
- 2017
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In: The European Conference on Lasers and Electro-Optics, CLEO_Europe 2017. - 9781509067367 ; Part F82-CLEO_Europe 2017
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Conference paper (peer-reviewed)abstract
- We present a compact HHG source driven by a few-cycle, few μJ, 200 kHz OPCPA system. Efficient harmonics are generated from Neon, Argon and Krypton with conversion efficiency of 4.0×10-8, 1.2×10-6 and 4.1×10-6, respectively.
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| 8. |
- Guo, Chen, et al.
(author)
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Phase control of attosecond pulses in a train
- 2018
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3
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Journal article (peer-reviewed)abstract
- Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.
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| 9. |
- Guo, Chen, et al.
(author)
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Single-shot, high-repetition rate carrier-envelope-phase detection of ultrashort laser pulses
- 2023
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In: Optics Letters. - 0146-9592. ; 48:20, s. 5431-5434
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Journal article (peer-reviewed)abstract
- We propose a single-shot, high-repetition rate measurement scheme of the carrier-envelope phase offset of ultrashort laser pulses. The spectral fringes resulting from f-2f nonlinear interferometry, encoding the carrier-envelope-phase, are evaluated completely optically via an optical Fourier transform. For demonstration, the carrier-envelope-phase of a 200 kHz, few-cycle optical parametric chirped-pulse amplification (OPCPA) laser system was measured employing an interferometer as a periodic optical filter. The proposed method shows excellent agreement with simultaneous measurement of the spectral fringes by a fast line-scan camera.
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| 10. |
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| 11. |
- Harth, Anne, et al.
(author)
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Compact 200 kHz HHG source driven by a few-cycle OPCPA
- 2018
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In: Journal of Optics (United Kingdom). - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 20:1
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Journal article (peer-reviewed)abstract
- We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ∼10-6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.
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| 12. |
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| 13. |
- Lorek, Eleonora, et al.
(author)
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Size and shape dependent few-cycle near-field dynamics of bowtie nanoantennas
- 2015
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In: Optics Express. - 1094-4087. ; 23:24, s. 31460-31471
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Journal article (peer-reviewed)abstract
- Metal nanostructures can transfer electromagnetic energy from femtosecond laser pulses to the near-field down to spatial scales well below the optical diffraction limit. By combining few-femtosecond laser pulses with photoemission electron microscopy, we study the dynamics of the induced few-cycle near-field in individual bowtie nanoantennas. We investigate how the dynamics depend on antenna size and exact bowtie shape resulting from fabrication. Different dynamics are, as expected, measured for antennas of different sizes. However, we also detect comparable dynamics differences between individual antennas of similar size. With Finite-difference time-domain simulations we show that these dynamics differences between similarly sized antennas can be due to small lateral shape variations generally induced during the fabrication.
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| 14. |
- Matyschok, Jan, et al.
(author)
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Compact, high-repetition-rate OPCPA system for high harmonic generation
- 2014
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In: Frontiers in Ultrafast Optics : Biomedical, Scientific, and Industrial Applications XIV - Biomedical, Scientific, and Industrial Applications XIV. - : SPIE. - 9780819498854 ; 8972
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Conference paper (peer-reviewed)abstract
- A compact, high-repetition rate optical parametric chirped pulse amplifier system emitting CEP-stable, few-cycle pulses with 10 μJ of pulse energy is reported for the purpose of high-order harmonic generation. The system is seeded from a commercially available, CEP-stabilized Ti:sapphire oscillator, delivering an octave-spanning spectrum from 600-1200 nm. The oscillator output serves on the one hand as broadband signal for the parametric amplification process and on the other hand as narrowband seed for an Ytterbium-based fiber preamplifier with subsequent main amplifiers and frequency doubling. Broadband parametric amplification up to 17 μJ at 200 kHz repetition rate was achieved in two 5 mm BBO crystals using non-collinear phase matching in the Poynting-vector-walk-off geometry. Efficient pulse compression down to 6.3 fs is achieved with chirped mirrors leading to a peak power exceeding 800 MW. We observed after warm-up time a stability of < 0.5 % rms over 100 min. Drifts of the CE-phase in the parametric amplifier part could be compensated by a slow feedback to the set point of the oscillator phase lock. The CEP stability was measured to be better than 80 mrad over 15 min (3 ms integration time). The experimentally observed output spectra and energies could be well reproduced by simulations of the parametric amplification process based on a (2+1)-dimensional nonlinear propagation code, providing important insight for future repetition rate scaling of OPCPA systems. The system is well-suited for attosecond science experiments which benefit from the high repetition rate. First results for high-order harmonic generation in argon will be presented.
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| 15. |
- Matyschok, Jan, et al.
(author)
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Temporal and spatial effects inside a compact and CEP stabilized, few-cycle OPCPA system at high repetition rates
- 2013
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In: Optics Express. - 1094-4087. ; 21:24, s. 29656-29665
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Journal article (peer-reviewed)abstract
- We present a compact and ultra-stable few-cycle OPCPA system. In two non-collinear parametric amplification stages pulse energies up to 17 mu J at 200 kHz repetition rate are obtained. Recompression of the broadband pulses down to 6.3 fs is performed with chirped mirrors leading to peak powers above 800 MW. The parametric amplification processes were studied in detail employing (2 + 1) dimensional numerical simulations and compared to experimental observations in terms of spectral shapes, pulse energy, spatial effects as well as delay dependent nonlinear mixing products. This gives new insights into the parametric process and design guidelines for high repetition rate OPCPA systems. (C) 2013 Optical Society of America
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| 16. |
- Mikaelsson, Sara, et al.
(author)
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A high-repetition rate attosecond light source for time-resolved coincidence spectroscopy
- 2020
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In: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614 .- 2192-8606. ; 10:1, s. 117-128
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Journal article (peer-reviewed)abstract
- Attosecond pulses, produced through high-order harmonic generation in gases, have been successfully used for observing ultrafast, subfemtosecond electron dynamics in atoms, molecules and solid state systems. Today's typical attosecond sources, however, are often impaired by their low repetition rate and the resulting insufficient statistics, especially when the number of detectable events per shot is limited. This is the case for experiments, where several reaction products must be detected in coincidence, and for surface science applications where space charge effects compromise spectral and spatial resolution. In this work, we present an attosecond light source operating at 200 kHz, which opens up the exploration of phenomena previously inaccessible to attosecond interferometric and spectroscopic techniques. Key to our approach is the combination of a high-repetition rate, few-cycle laser source, a specially designed gas target for efficient high harmonic generation, a passively and actively stabilized pump-probe interferometer and an advanced 3D photoelectron/ion momentum detector. While most experiments in the field of attosecond science so far have been performed with either single attosecond pulses or long trains of pulses, we explore the hitherto mostly overlooked intermediate regime with short trains consisting of only a few attosecond pulses. We also present the first coincidence measurement of single-photon double-ionization of helium with full angular resolution, using an attosecond source. This opens up for future studies of the dynamic evolution of strongly correlated electrons.
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| 17. |
- Mikaelsson, Sara, et al.
(author)
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A high-repetition rate attosecond light source for time-resolved coincidence spectroscopy
- 2021
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In: Frontiers in Optics and Photonics. - : De Gruyter. - 9783110710687 - 9783110709735 ; , s. 119-130
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Book chapter (peer-reviewed)abstract
- Attosecond pulses, produced through high-order harmonic generation in gases, have been successfully used for observing ultrafast, subfemtosecond electron dynamics in atoms, molecules and solid state systems. Today's typical attosecond sources, however, are often impaired by their low repetition rate and the resulting insufficient statistics, especially when the number of detectable events per shot is limited. This is the case for experiments, where several reaction products must be detected in coincidence, and for surface science applications where space charge effects compromise spectral and spatial resolution. In this work, we present an attosecond light source operating at 200 kHz, which opens up the exploration of phenomena previously inaccessible to attosecond interferometric and spectroscopic techniques. Key to our approach is the combination of a high-repetition rate, few-cycle laser source, a specially designed gas target for efficient high harmonic generation, a passively and actively stabilized pump-probe interferometer and an advanced 3D photoelectron/ion momentum detector. While most experiments in the field of attosecond science so far have been performed with either single attosecond pulses or long trains of pulses, we explore the hitherto mostly overlooked intermediate regime with short trains consisting of only a few attosecond pulses. We also present the first coincidence measurement of single-photon dou-ble-ionization of helium with full angular resolution, using an attosecond source. This opens up for future studies of the dynamic evolution of strongly correlated electrons.
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| 18. |
- Mikaelsson, Sara, et al.
(author)
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Spatio-temporal characterization and optimization of a 200-kHz OPCPA laser system
- 2018
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In: CLEO : Science and Innovations, CLEO_SI 2018 - Science and Innovations, CLEO_SI 2018. - 9781557528209 ; Part F94-CLEO_SI 2018
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Conference paper (peer-reviewed)abstract
- We present measurements on a few cycle OPCPA laser chain where due to careful characterization and compensation of the spectral phase and spatio-temporal couplings, we are able achieve efficient HHG with very low pulse energy.
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| 19. |
- Miranda, Miguel, et al.
(author)
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Fast iterative retrieval algorithm for ultrashort pulse characterization using dispersion scans
- 2017
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In: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 34:1, s. 190-197
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Journal article (peer-reviewed)abstract
- We present an iterative retrieval algorithm based on data constraint for ultrashort pulse characterization using dispersion scan (d-scan). The proposed algorithm is much faster and leads to a drastic reduction of retrieval times, but, compared to the standard algorithm, it performs less robustly in the retrieval of noisy d-scan traces. The algorithm is tested on several simulated cases and in two different experimental cases in the few-cycle regime.
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| 20. |
- Miranda, Miguel, et al.
(author)
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Measurement and correction of spectral phase in a few-cycle parametric amplifier
- 2018
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In: Ultrafast Optics 2017 : Abstract Book - Abstract Book. - 0277-786X .- 1996-756X. - 9781510617162 ; 10606, s. 75-75
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Conference paper (peer-reviewed)abstract
- We study the spectral phase introduced by parametric amplification and how high extraction efficiency of energy leads to deterioration of the phase. Avoiding this regime, and using a pulse shaper, we achieve high-contrast ultrashort pulses.
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| 21. |
- Miranda, Miguel, et al.
(author)
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Spatiotemporal characterization of ultrashort laser pulses using spatially resolved Fourier transform spectrometry
- 2014
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In: Optics Letters. - 0146-9592. ; 39:17, s. 5142-5145
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Journal article (peer-reviewed)abstract
- We present a method for characterizing ultrashort laser pulses in space and time, based on spatially resolved Fourier transform spectrometry. An unknown pulse is interfered with a delayed, spatially uniform reference on a CCD camera. The reference pulse is created by spatially filtering a portion of the unknown pulse. By scanning the delay between the two pulses, an interferogram is obtained at each pixel, allowing us to determine the spatially resolved phase difference between the unknown pulse and the reference pulse. High-resolution spatiotemporal characterization of an ultrashort pulse is demonstrated, and the sensitivity of the method to spatiotemporal coupling is shown for the case of a pulse with pulse front tilt. (C) 2014 Optical Society of America
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| 22. |
- Miranda, Miguel, et al.
(author)
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Spatiotemporal characterization of ultrashort optical vortex pulses
- 2017
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In: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 64:sup4, s. 1-6
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Journal article (peer-reviewed)abstract
- We use a spiral phase plate to generate few-cycle optical vortices from an ultrafast titanium:sapphire oscillator and characterize them in the spatiotemporal domain with a recently introduced technique based on spatially resolved Fourier transform spectrometry. The performance of this simple approach to the generation of optical vortices is analysed from a wavelength-dependent perspective as well as in the spatiotemporal domain, allowing us to characterize ultrashort vortex pulses in space, frequency and time.
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| 23. |
- Morgner, Uwe, et al.
(author)
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Few-cycle and phase stable OPCPA systems with high repetition rate
- 2015
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In: CLEO : Science and Innovations, CLEO-SI 2015 - Science and Innovations, CLEO-SI 2015. - 9781557529688
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Conference paper (peer-reviewed)abstract
- We present different approaches for high repetition rate, few-cycle pulse generation with μJ-level energy from compact OPCPA systems. The sources are based on octave spanning Ti:Sa oscillators with all-optical synchronization to state-of-the-art Ytterbium based amplifiers.
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| 24. |
- Mårsell, Erik, et al.
(author)
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Direct subwavelength imaging and control of near-field localization in individual silver nanocubes
- 2015
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 107:20
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Journal article (peer-reviewed)abstract
- We demonstrate the control of near-field localization within individual silver nanocubes through photoemission electron microscopy combined with broadband, few-cycle laser pulses. We find that the near-field is concentrated at the corners of the cubes, and that it can be efficiently localized to different individual corners depending on the polarization of the incoming light. The experimental results are confirmed by finite-difference time-domain simulations, which also provide an intuitive picture of polarization dependent near-field localization in nanocubes. (C) 2015 AIP Publishing LLC.
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| 25. |
- Mårsell, Erik, et al.
(author)
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Nanoscale imaging of local few-femtosecond near-field dynamics within a single plasmonic nanoantenna.
- 2015
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:10, s. 6601-6608
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Journal article (peer-reviewed)abstract
- The local enhancement of few-cycle laser pulses by plasmonic nanostructures opens up for spatiotemporal control of optical interactions on a nanometer and few-femtosecond scale. However, spatially resolved characterization of few-cycle plasmon dynamics poses a major challenge due to the extreme length and time scales involved. In this letter, we experimentally demonstrate local variations in the dynamics during the few strongest cycles of plasmon-enhanced fields within individual rice-shaped silver nanoparticles. This was done using 5.5 fs laser pulses in an interferometric time-resolved photoemission electron microscopy setup. The experiments are supported by finite-difference time-domain simulations of similar silver structures. The observed differences in the field dynamics across a single particle do not reflect differences in plasmon resonance frequency or dephasing time. They instead arise from a combination of retardation effects and the coherent superposition between multiple plasmon modes of the particle, inherent to a few-cycle pulse excitation. The ability to detect and predict local variations in the few-femtosecond time evolution of multi-mode coherent plasmon excitations in rationally synthesized nanoparticles can be used in the tailoring of nanostructures for ultrafast and nonlinear plasmonics.
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