| 1. |
- Arnold, Cord L., et al.
(författare)
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Spatiotemporal coupling of attosecond pulses
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. - 9781728104690 ; Part F140-CLEO_Europe 2019
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Konferensbidrag (refereegranskat)abstract
- Attosecond pulses in the extreme ultraviolet (XUV) spectral range are today routinely generated via high-order harmonic generation (HHG), when intense ultrashort laser pulses are focused into a gaseous generation medium. The effect is most easily understood in a semi-classical picture [1]. An electron can tunnel ionize from the distorted atomic potential, pick up kinetic energy in the laser field, potentially return to its parent ion and recombine. The excess energy is emitted as XUV photon. The process repeats for every half-cycle of the driving field, resulting in a train of attosecond pulses and in the frequency domain in the well-known, odd-order comb of harmonics. Two main families of electron trajectories leading to the same photon energy can be distinguished into 'short' and 'long', according to their time of travel in the continuum. Due to the complicated nature of the HHG process, attosecond pulses usually cannot be separated into their temporal and spatial profiles, but instead have strong chromatic aberration and are spatio-temporally coupled [2-4].
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| 2. |
- Hergert, G., et al.
(författare)
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Femtosecond streaking and control of electrons from a plasmonic nanofocusing taper by photoemitted charges in a nanoantenna
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. - 9781728104690
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Konferensbidrag (refereegranskat)abstract
- Manipulation of electrons by light forms the basis for future optoelectronic devices targeting switching speeds close to optical frequencies. Specifically, nanolocalized optical and plasmonic fields play a key role as they reduce the interaction region down to few nanometers and thus the time electrons require to traverse the fields. In this context, the precise knowledge of the localized fields is an important prerequisite, and their metrology as well as the control of electrons in near fields are active research areas [1,2].
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| 3. |
- Johansson, Alexandra C., 1987-, et al.
(författare)
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Precise comb-based fourier transform spectroscopy for line parameter retrieval
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference (CLEO/EUROPE-EQEC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781728104690
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Konferensbidrag (refereegranskat)abstract
- Accurate parameters of molecular transitions are needed for data analysis in many applications, ranging from atmospheric research to astrophysics and determination of fundamental constants. Optical frequency comb Fourier transform spectroscopy (OFC-FTS) is particularly well-suited for high-precision measurements of broadband molecular spectra. From these spectra, the parameters of individual transitions - all measured simultaneously under the same experimental conditions - can be determined. We use a mechanical OFC-FTS spectrometer with sub-nominal resolution [1, 2] to perform precise broadband measurements of entire molecular bands of CO2 using either direct absorption spectroscopy or cavity-enhanced complex refractive index spectroscopy (CE-CRIS) [3] and we extract line parameters for line shapes beyond the Voigt profile.
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| 4. |
- Kores, Cristine C., et al.
(författare)
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Spectral response of distributed-feedback resonators with a continuously distributed phase shift
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society.
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Konferensbidrag (refereegranskat)abstract
- Distributed-feedback (DFB) resonators [1, 2] are of interest for inherently producing narrow-linewidth laser emission, without the need of external cavities or filters. The single-frequency emission is obtained by designing an additional phase shift δϕdesign of π/2, thereby producing a resonance that is spectrally located at the centre of the reflection band. Conventionally, δϕdesign is introduced abruptly in the Bragg grating, but this method has the important disadvantage of causing spatial-hole burning in the laser resonator due to a high photon density where the phase shift is located. An attractive solution is to distribute the phase shift, e.g. by widening the waveguide region, thus increasing the effective refractive index [3].
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| 5. |
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| 6. |
- Lahuillier, Anne
(författare)
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An introduction to attosecond pulses and attosecond physics
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. - 9781728104690
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Konferensbidrag (refereegranskat)abstract
- The interaction of atoms with intense laser radiation leads to the generation of high-order harmonics of the laser field. In the time domain, this corresponds to a train of pulses in the extreme ultraviolet range and with attosecond duration. This tutorial will introduce the physics of high-order harmonic generation and attosecond pulses.
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| 7. |
- Mikaelsson, Sara, et al.
(författare)
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Controlled asymmetric photoelectron emission using electron wavepacket interference
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. - 9781728104690
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Konferensbidrag (refereegranskat)abstract
- Two-color ionization is a powerful method for characterizing light fields and investigating atomic and molecular physics with attosecond sources based on High Harmonic Generation (HHG). Depending on the time duration of the light fields, two main techniques have been established: streaking [1], appropriate in the regime where a single attosecond pulse is generated, and RABBIT, used instead when a relatively long fundamental pulse generates an XUV pulse train and the variation between consecutive XUV pulses is negligible [2]. In the regime where high harmonics are generated by a few-cycle fundamental pulse, however, both the amplitude and phase of the few resulting XUV pulses vary significantly, and this variation can be controlled by the CEP of the driving IR field [3]. In this work, we use attosecond pulse trains produced by HHG in argon using a 200 kHz-repetition rate, Carrier-Envelope-Phase (CEP) stable, 6-fs OPCPA laser system [4] and detect emitted photoelectrons from helium byby a three-dimensional (3D) momentum spectrometer [5]. With our excitation scheme, where a weak replica of the generating IR is overlapped with the short XUV pulse train for photoionization, we investigate the regime between the two limits represented by streaking and RABBIT.
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| 8. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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THz time-domain reflection spectroscopy of KTiOPO4
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Terahertz (THz) radiation has been of increasing interest in the last decades, for security, manufacturing, quality control, medical and security imaging applications. The field requires more efficient and affordable sources and nonlinear upconversion schemes point in this direction. KTiOPO, (KTP) is a well-established material for nonlinear optical applications in the visible and near-IR region thanks to its large transparency, high nonlinear coefficient and damage threshold. Its reasonably low absorption [1, 2] and strong polariton resonances [1] show promise for efficient IR to THz upconversion and Wu et al. [2] recently demonstrated its superiority to LiNbO3 and LiTaO3 in a back to back experiment. However, the complex refractive index needs to be measured before further power scaling is realistic.
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| 9. |
- Sadiek, Ibrahim, et al.
(författare)
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Optical frequency comb photoacoustic spectroscopy
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781728104690
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Konferensbidrag (refereegranskat)abstract
- Photoacoustic spectroscopy (PAS) based on continuous wave (cw) lasers provides high absorption sensitivity in small sample volume [1, 2] but it is usually restricted to single species detection because of the limited tunability of cw lasers. Broadband PAS has been demonstrated using cantilever-enhanced detectors in combination with incoherent [3] or supercontinuum [4] light sources modulated by conventional Fourier transform spectrometers (FTS), however, the spectral resolution was limited to a few cm-1. Here we report the first demonstration of optical frequency comb photoacoustic spectroscopy (OFC-PAS), which combines the wide spectral coverage and high resolution of frequency combs with the small sample volume of photoacoustic detection [5].
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| 10. |
- Schell, A. W., et al.
(författare)
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Investigation of the spectroscopic properties of single defects in hexagonal boron nitride
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Among the quantum systems capable of emitting single photons, the class of recently discovered defects in hexagonal boron nitride (hBN) is especially interesting, as these defects offer much desired characteristics such as narrow emission lines and photostability [1]. Like for any new class of quantum emitters, the first challenges to solve are the understanding of their photophysics as well as to find ways to facilitate integration in photonics structures. Here, we will show our investigation of the optical transition in hBN with different methods: Employing excitation with a short laser pulse the emission properties in case of linear and non-linear excitation can be compared [2]. We find clear antibunching signals that prove the single emitter character in both excitation cases. To gain further knowledge, we also obtain saturation curves. From a comparison of one- and two-photon case insights about the level structure of the defects can be obtained. The possibility to perform two-photon excitation makes this single photon emitter an interesting candidate as a biosensor.
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