| 1. |
- Gautam, Rekha, et al.
(författare)
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Nonlinear optical response and self-trapping of light in biological suspensions
- 2020
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Ingår i: ADVANCES IN PHYSICS-X. - : TAYLOR & FRANCIS LTD. - 2374-6149. ; 5:1
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Forskningsöversikt (refereegranskat)abstract
- In the past decade, the development of artificial materials exhibiting novel optical properties has become a major scientific endeavor. One particularly interesting system is synthetic soft matter, which plays a central role in numerous fields ranging from life sciences, chemistry to condensed matter and biophysics. In this paper, we review briefly the optical force-induced nonlinearities in colloidal suspensions, which can give rise to nonlinear self-trapping of light for enhanced propagation through otherwise highly scattering media such as dielectric and plasmonic nanosuspensions. We then focus on discussing our recent work with respect to nonlinear biological suspensions, including self-trapping of light in colloidal suspensions of marine bacteria and red blood cells, where the nonlinear response is largely attributed to the optical forces acting on the cells. Although it is commonly believed that biological media cannot exhibit high optical non-linearity, self-focusing of light and formation of soliton-like wave-guides in bio-soft matter have been observed. Furthermore, we present preliminary results on biological waveguiding and sensing, and discuss some perspectives towards biomedical applications. The concept may be developed for subsequent studies and techniques in situations when low scattering and deep penetration of light is desired.
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| 2. |
- Li, Zhipeng, et al.
(författare)
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Nanoantenna effect of surface-enhanced Raman scattering : managing light with plasmons at the nanometer scale
- 2016
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Ingår i: Advances in Physics: X. - : Informa UK Limited. - 2374-6149. ; 1:3, s. 492-521
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Forskningsöversikt (refereegranskat)abstract
- Manipulating light on the nanometer scale is a challenging topic not only from a fundamental point of view, but also for applications aiming toward the design of miniature optical devices. Nanoplasmonics is a rapidly emerging branch of photonics, which offers variable means to manipulate light using surface plasmon excitations on metal nanostructures. As a spectroscopic phenomenon discovered nearly 40 years ago, surface-enhanced Raman scattering (SERS) has been an active topic of fundamental and applied researches. The dominating electromagnetic enhancement in SERS is caused by surface plasmon resonances. This is a typical example of manipulating light intensity with plasmons. Here, we will review the recent SERS studies related to nanoantenna effects on different metal nanostructures based on electromagnetic enhancement. Three aspects will be the focus in this paper: (1) the coupled nanostructures which act as receiving and emitting antenna that can generate enormous SERS enhancement ~E4 even enough for single molecule SERS. (2) The polarization of SERS at the single molecule limit, including the linear and circular polarizations can be manipulated using designed asymmetric antennas. Such an effect can make the traditional 1/2 and 1/4 wave plates miniaturized to the nanometer scale. (3) Combining nanoantenna and waveguiding effects, remote excitation of SERS can be realized, which may open a new area of single molecule SERS on nanophotonic circuits.
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| 3. |
- Luo, Sizuo, et al.
(författare)
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Ultra-stable and versatile high-energy resolution setup for attosecond photoelectron spectroscopy
- 2023
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Ingår i: Advances in Physics: X. - 2374-6149. ; 8:1
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Forskningsöversikt (refereegranskat)abstract
- Attosecond photoelectron spectroscopy has opened up for studying light–matter interaction on ultrafast time scales. It is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline based on a Mach-Zehnder interferometer. The active stabilization keeps the interferometer ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning range of (Formula presented.) fs. A tunable femtosecond laser source to drive high-order harmonic generation allows for precisely addressing atomic and molecular resonances. Furthermore, the interferometer includes a spectral shaper in 4f-geometry in the probe arm as well as a tunable bandpass filter in the pump arm, which offer additional high flexibility in terms of tunability as well as narrowband or polychromatic probe pulses. We demonstrate the capabilities of the beamline via experiments using several variants of the RABBIT (reconstruction of attosecond beating by two photon transitions) technique. In this setup, the temporal-spectral resolution of photoelectron spectroscopy can reach a new level of accuracy and precision.
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| 4. |
- Nagy, Tamas, et al.
(författare)
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High-energy few-cycle pulses: post-compression techniques
- 2021
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Ingår i: Advances in Physics: X. - : Taylor & Francis. - 2374-6149. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Contemporary ultrafast science requires reliable sources of high-energy few-cycle light pulses. Currently two methods are capable of generating such pulses: post compression of short laser pulses and optical parametric chirped-pulse amplification (OPCPA). Here we give a comprehensive overview on the post-compression technology based on optical Kerr-effect or ionization, with particular emphasis on energy and power scaling. Relevant types of post compression techniques are discussed including free propagation in bulk materials, multiple-plate continuum generation, multi-pass cells, filaments, photonic-crystal fibers, hollow-core fibers and self-compression techniques. We provide a short theoretical overview of the physics as well as an in-depth description of existing experimental realizations of post compression, especially those that can provide few-cycle pulse duration with mJ-scale pulse energy. The achieved experimental performances of these methods are compared in terms of important figures of merit such as pulse energy, pulse duration, peak power and average power. We give some perspectives at the end to emphasize the expected future trends of this technology.
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| 5. |
- Nilsson, Anders, et al.
(författare)
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Probing water with X-ray lasers
- 2016
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Ingår i: Advances in physics: X. - : Informa UK Limited. - 2374-6149. ; 1:2, s. 226-245
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Forskningsöversikt (refereegranskat)abstract
- Here, we discuss three cases where the X-ray free-electron laser, the Linac Coherent Light Source, has been used to probe water. The ability to cool water very rapidly down to 227 K and to probe it with ultrashort (50 fs) X-ray pulses before freezing has allowed for investigating water structure below the previous limit of homogeneous ice nucleation. It was found that at the temperature where the thermodynamic response functions, such as heat capacity and isothermal compressibility, seem to diverge there is no discontinuous change in structure, but instead an accelerated transformation from a disordered state to a strongly tetrahedral. The ice nucleation rate in bulk-like micron-sized water droplets could be determined for temperatures down to 227 K and was shown to be similar to 8 orders of magnitude lower than previous data for nanodroplets. The application to X-ray spectroscopy is discussed based on measurements at high X-ray fluence where multiple valence-hole states can be generated. Finally, a perspective to the future is presented regarding X-ray photon correlation spectroscopy with which true equilibrium dynamical properties can be studied.
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