The Experts below are selected from a list of 3723 Experts worldwide ranked by ideXlab platform
Alfred J Meixner - One of the best experts on this subject based on the ideXlab platform.
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simulation of a metallic snom tip illuminated by a Parabolic Mirror
Optics Express, 2013Co-Authors: Josip Mihaljevic, Christian Hafner, Alfred J MeixnerAbstract:We investigate numerically a Scanning Near field Optical Microscope (SNOM) that uses a Parabolic Mirror (PM) to focus a radially polarized beam on a metallic tip. In order to overcome problems - like overestimated near fields or resonances - that arise when only considering finite tips, we have introduced a semi-infinite continuation of the tip, which incorporates the analytic solution of surface waves. For a realistic modeling the right description of the incident field is essential and we have complied with this requirement by a Bessel expansion of the focal fields, which is also applicable to an aplanatic objective. The established numerical model is used for an extensive study of model parameters like tip geometry, illumination directions and tip materials (Ag, Au, Al and Cu). Compared with a simplified inverted microscope configuration, the PM setup shows an increased field enhancement (factor of 2–2.5), which can be ascribed to the efficient coupling of the exciting field to tip surface plasmons.
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Tighter focusing with a Parabolic Mirror
Optics Letters, 2008Co-Authors: J. Stadler, Constantin Stanciu, C. Stupperich, Alfred J MeixnerAbstract:We demonstrate experimentally and theoretically that a Parabolic Mirror (PM) with a high numerical aperture (NA) of 1 focuses a radially polarized laser mode to the smallest diffraction-limited spot at a fixed NA and wavelength, having an area of 0.134 lambda(2). The measurements were performed with a confocal microscope, using the PM as a focusing and collecting element. The results stand in accordance with the theoretical calculations presented by Davidson and Bokor [Opt. Lett. 29, 1318 (2004)], who predicted a reduction in the total focal spot size of 43% as compared with an aplanatic lens.
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High NA particle- and tip-enhanced nanoscale Raman spectroscopy with a Parabolic-Mirror microscope
Journal of Microscopy, 2008Co-Authors: Constantin Stanciu, M. Sackrow, Alfred J MeixnerAbstract:Detecting efficiently the plasmon-enhanced Raman signal of molecules created in the nanometre-sized gap between a metal nanoparticle or the apex of a sharp tip and a metal surface is the key problem in particle- or tip-enhanced local surface spectroscopy (Pettinger et al., 2004; Roth et al., 2006). The optical excitation field has to be polarized along the gap, and the field emerging from the gap has to be observed from the side. These geometrical restrictions usually limit the numerical aperture of the lens used for exciting the gap and collecting the scattered photons created in the gap. We present a novel method to overcome this problem. The solution is based on a confocal optical microscope with a high numerical aperture Parabolic Mirror for excitation and detection. Localized plasmons can be efficiently excited parallel to the surface normal by illuminating the Parabolic Mirror with a radially polarized doughnut mode and the field emerging sidewise from the gap can be efficiently collected by the rim of the Parabolic Mirror and directed to the detection system. First results on particle- and tip-enhanced Raman spectroscopic measurements of benzotriazole molecules adsorbed on gold films are presented.
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confocal microscopy with a high numerical aperture Parabolic Mirror
Optics Express, 2001Co-Authors: A Drechsler, Alfred J Meixner, M A Lieb, C Debus, G TarrachAbstract:A novel high-resolution stage scanning confocal microscope for fluorescence microscopy and spatially resolved spectroscopy with a high numerical aperture (NA≈1) Parabolic Mirror objective is investigated. A spatial resolution close to the diffraction limit is achieved. As microscopic fluorescent test objects, dye-loaded zeolite microcrystals (diameter approx. 0.4 µm) and single fluorescent molecules were used. Confocal fluorescence images show a spatial resolution of Δx=0.8·λ both at room temperature and at 1.8 K. Imaging of a quasi-point light source and focusing by the Parabolic Mirror were investigated experimentally and theoretically. Deviations between the theoretical results for a perfect Parabolic Mirror and the experimental results can be attributed to small deviations of the Mirror profile from an ideal parabola.
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a high numerical aperture Parabolic Mirror as imaging device for confocal microscopy
Optics Express, 2001Co-Authors: M A Lieb, Alfred J MeixnerAbstract:We explore the diffraction limited focusing and confocal imaging properties of a high NA Parabolic Mirror for confocal imaging and spectroscopy of nanoparticles and single molecules. Vector field calculations of the electric fields near focus for both linear and radially polarized illumination are discussed and show that the optical field can be similar tightly focused as in the case of a high NA objective lens. Furthermore they show that a high NA Parabolic Mirror allows an easy orientation of the polarization of the illuminating light in all spatial directions. The simulation of confocal imaging of single molecules is discussed and yields, that the use of radially polarized excitation light gives an easy access to their orientations.
Gerd Leuchs - One of the best experts on this subject based on the ideXlab platform.
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single photons emitted by nanocrystals optically trapped in a deep Parabolic Mirror
Physical Review Letters, 2020Co-Authors: Markus Sondermann, Gerd Leuchs, Vsevolod Salakhutdinov, Luigi Carbone, E Giacobino, A BramatiAbstract:We investigate the emission of single photons from $\mathrm{CdSe}/\mathrm{CdS}$ dots-in-rod which are optically trapped in the focus of a deep Parabolic Mirror. Thanks to this Mirror, we are able to image almost the full $4\ensuremath{\pi}$ emission pattern of nanometer-sized elementary dipoles and verify the alignment of the rods within the optical trap. From the motional dynamics of the emitters in the trap, we infer that the single-photon emission occurs from clusters comprising several emitters. We demonstrate the optical trapping of rod-shaped quantum emitters in a configuration suitable for efficiently coupling an ensemble of linear dipoles with the electromagnetic field in free space.
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focusing light with a deep Parabolic Mirror
arXiv: Optics, 2019Co-Authors: Norbert Lindlein, Markus Sondermann, Hildegard Konermann, Ulf Peschel, Robert Maiwald, Gerd LeuchsAbstract:The smallest possible focus is achieved when the focused wave front is the time reversed copy of the light wave packet emitted from a point in space (S. Quabis et al., Opt. Commun. 179 (2000) 1-7). The best physical implementation of such a pointlike sub-wavelength emitter is a single atom performing an electric dipole transition. In a former paper (N. Lindlein et al., Laser Phys. 17 (2007) 927-934) we showed how such a dipole-like radiant intensity distribution can be produced with the help of a deep Parabolic Mirror and appropriate shaping of the intensity of the radially polarized incident plane wave. Such a dipole wave only mimics the far field of a linear dipole and not the near field components. Therefore, in this paper, the electric energy density in the focus of a Parabolic Mirror is calculated using the Debye integral method. Additionally, a comparison with "conventional nearly 4pi" illumination using two high numerical aperture objectives is performed. The influence of aberrations due to a misalignment of the incident plane wave is discussed.
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optical trapping of nanoparticles by full solid angle focusing
arXiv: Optics, 2015Co-Authors: Vsevolod Salakhutdinov, Markus Sondermann, Luigi Carbone, E Giacobino, A Bramati, Gerd LeuchsAbstract:Optical dipole-traps are used in various scientific fields, including classical optics, quantum optics and biophysics. Here, we propose and implement a dipole-trap for nanoparticles that is based on focusing from the full solid angle with a deep Parabolic Mirror. The key aspect is the generation of a linear-dipole mode which is predicted to provide a tight trapping potential. We demonstrate the trapping of rod-shaped nanoparticles and validate the trapping frequencies to be on the order of the expected ones. The described realization of an optical trap is applicable for various other kinds of solid-state targets. The obtained results demonstrate the feasibility of optical dipole-traps which simultaneously provide high trap stiffness and allow for efficient interaction of light and matter in free space.
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qed with a Parabolic Mirror
Physical Review A, 2013Co-Authors: G Alber, Gerd Leuchs, Jozsef Zsolt Bernad, Magdalena Stobinska, L L SanchezsotoAbstract:We investigate the quantum electrodynamics of a single two-level atom located at the focus of a Parabolic cavity. We first work out the modifications of the spontaneous emission induced by the presence of this boundary in the optical regime, where the dipole and the rotating-wave approximations apply. Furthermore, the single-photon state that leaves the cavity asymptotically is determined. The corresponding time-reversed single-photon quantum state is capable of exciting the atom in this extreme multimode scenario with near-unit probability. Using semiclassical methods, we derive a photon-path representation for the relevant transition amplitudes and show that it constitutes a satisfactory approximation for a wide range of wavelengths.
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single ion trapped in the focal spot of a deep Parabolic Mirror
Conference on Lasers and Electro-Optics, 2012Co-Authors: Andrea Golla, Markus Sondermann, Robert Maiwald, Martin Fischer, Marianne Bader, Benoit Chalopin, Gerd LeuchsAbstract:We report on trapping of single Ytterbium ions in the focal spot of a deep Parabolic Mirror providing a setup for efficient free space photon atom coupling. Additionally issues regarding imaging, ion localization and fluorescence collection are discussed.
Emmanuel Guillot - One of the best experts on this subject based on the ideXlab platform.
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5 5 w continuous wave tem 00 mode nd yag solar laser by a light guide 2v shaped pump cavity
Applied Physics B, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, R Bouadjemine, Emmanuel GuillotAbstract:A significant progress in TEM00-mode solar laser power and efficiency with heliostat–Parabolic Mirror system is reported here. A double-stage light-guide/2V-shaped pump cavity is used to efficiently couple and redistribute the concentrated pump light from a 2-m-diameter Parabolic Mirror to a 4-mm-diameter, 30-mm-length, 1.1 at.% Nd:YAG single-crystal rod. The light guide with large rectangular cross section enables a stable uniform pumping profile along the laser rod, resulting also in an enhanced tracking error compensation capacity. 5.5 W cw TEM00-mode solar laser power was measured at the output of a thermally near unstable asymmetric resonator. 150 and 157 % improvement in TEM00-mode solar laser collection efficiency and slope efficiency were obtained, respectively.
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56 w cw nd yag solar laser by a heliostat Parabolic Mirror system
European Quantum Electronics Conference, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, Emmanuel GuillotAbstract:Solar-pumped lasers are natural candidates for applications where sunlight is plentiful and few other energy sources are available. Since the first report of “A sun-pumped cw one-watt laser” in 1966 [1], optical and laser material advances have continued to improve solar laser performance. Parabolic Mirrors have long been explored to achieve tight focusing of incoming solar radiation. However, their use for solar laser researches has been neglected in recent years due to the increased interests in large-size Fresnel lenses. Fresnel lens is cost-effective, but it causes the dispersion of the solar radiation along its focal zone, hampering the efficient light concentration to the laser rod. It is therefore valuable for us to carry out the solar laser research with Parabolic Mirrors. A new progress in both solar laser collection efficiency and slope efficiency with heliostat - Parabolic Mirror system is reported here.
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highly efficient end side pumped nd yag solar laser by a heliostat Parabolic Mirror system
Applied Optics, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, Emmanuel GuillotAbstract:We report a large improvement in the collection and slope efficiency of an Nd:YAG solar laser pumped by a heliostat–Parabolic Mirror system. A conical fused silica lens was used to further concentrate the solar radiation from the focal zone of a 2 m diameter primary concentrator to a Nd:YAG single-crystal rod within a conical pump cavity, which enabled multipass pumping to the active medium. A 56 W cw laser power was measured, corresponding to 21.1 W/m2 record-high solar laser collection efficiency with the heliostat–Parabolic Mirror system. 4.9% slope efficiency was calculated, corresponding to 175% enhancement over our previous result.
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solar pumped tem00 mode nd yag laser by a heliostat Parabolic Mirror system
Solar Energy Materials and Solar Cells, 2015Co-Authors: Dawei Liang, Joana Almeida, Claudia R Vistas, Emmanuel GuillotAbstract:Abstract Here we report a significant advance in solar-pumped laser beam brightness by pumping a 3 mm diameter Nd:YAG single-crystal rod with a heliostat-Parabolic Mirror system. The incoming solar radiation is first collected and focused by the system. A rectangular fused silica light guide and a 2D-CPC concentrator are then combined to further compress the concentrated solar radiation into the laser rod within a V-shaped pumping cavity. 4.4 W continuous-wave TEM 00 mode ( M 2 ≤1.05) 1064 nm solar laser power is finally produced, attaining 4.0 W laser beam brightness figure of merit, which is 2.1 times higher than the previous record by a Fresnel lens. 0.81% TEM 00 mode laser slope efficiency is achieved.
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a 40 w cw nd yag solar laser pumped through a heliostat a Parabolic Mirror system
Laser Physics, 2013Co-Authors: Joana Almeida, Dawei Liang, Emmanuel Guillot, Yasser A AbdelhadiAbstract:Solar-pumped solid-state lasers are promising for renewable extreme-temperature material processing. Here, we report a significant improvement in solar laser collection efficiency by pumping the most widely used Nd:YAG single-crystal rod through a heliostat?Parabolic Mirror system. A conical-shaped fused silica light guide with 3D-CPC output end is used to both transmit and compress the concentrated solar radiation from the focal zone of a 2?m diameter Parabolic Mirror to a 5?mm diameter Nd:YAG rod within a conical pump cavity, which enables multi-pass pumping through the laser rod. 40?W cw laser power is measured, corresponding to 13.9?W?m?2 record-high collection efficiency for the solar laser pumped through a heliostat?Parabolic Mirror system. 2.9% slope efficiency is fitted, corresponding to 132% enhancement over that of our previous pumping scheme. A 209% reduction in threshold pump power is also registered.
Constantin Stanciu - One of the best experts on this subject based on the ideXlab platform.
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Parabolic Mirror-assisted tip-enhanced spectroscopic imaging for non-transparent materials
Journal of Raman Spectroscopy, 2009Co-Authors: D Zhang, Constantin Stanciu, Kai Braun, Laura Hennemann, Holger Hintz, Monika Fleischer, Hans-joachim Egelhaaf, Christoph J. Brabec, Dieter P. KernAbstract:A versatile and efficient tip-enhanced spectroscopic imaging technique based on a Parabolic Mirror (PM) assisted near-field optical microscope is demonstrated. The replacement of the conventional objective lens with a Parabolic Mirror allows the non-restricted investigation of sample materials regarding their opacity. In addition, an improved signal collection efficiency and effective excitation of the longitudinal plasmonic oscillation in the tip apex are obtained. The capabilities of PM-assisted tip-enhanced Raman (TER) and photoluminescence (PL) imaging in distinguishing the individual domains made of different chemical components in poly (3-hexythiophene)/[6, 6]-penyl-C 61 butyric acid methyl ester (P3HT/PCBM) solar cell blend film and in the investigation of the plasmonic properties of geometrically well-defined Au cones are demonstrated. © 2009 John Wiley & Sons, Ltd.
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Tighter focusing with a Parabolic Mirror
Optics Letters, 2008Co-Authors: J. Stadler, Constantin Stanciu, C. Stupperich, Alfred J MeixnerAbstract:We demonstrate experimentally and theoretically that a Parabolic Mirror (PM) with a high numerical aperture (NA) of 1 focuses a radially polarized laser mode to the smallest diffraction-limited spot at a fixed NA and wavelength, having an area of 0.134 lambda(2). The measurements were performed with a confocal microscope, using the PM as a focusing and collecting element. The results stand in accordance with the theoretical calculations presented by Davidson and Bokor [Opt. Lett. 29, 1318 (2004)], who predicted a reduction in the total focal spot size of 43% as compared with an aplanatic lens.
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High NA particle- and tip-enhanced nanoscale Raman spectroscopy with a Parabolic-Mirror microscope
Journal of Microscopy, 2008Co-Authors: Constantin Stanciu, M. Sackrow, Alfred J MeixnerAbstract:Detecting efficiently the plasmon-enhanced Raman signal of molecules created in the nanometre-sized gap between a metal nanoparticle or the apex of a sharp tip and a metal surface is the key problem in particle- or tip-enhanced local surface spectroscopy (Pettinger et al., 2004; Roth et al., 2006). The optical excitation field has to be polarized along the gap, and the field emerging from the gap has to be observed from the side. These geometrical restrictions usually limit the numerical aperture of the lens used for exciting the gap and collecting the scattered photons created in the gap. We present a novel method to overcome this problem. The solution is based on a confocal optical microscope with a high numerical aperture Parabolic Mirror for excitation and detection. Localized plasmons can be efficiently excited parallel to the surface normal by illuminating the Parabolic Mirror with a radially polarized doughnut mode and the field emerging sidewise from the gap can be efficiently collected by the rim of the Parabolic Mirror and directed to the detection system. First results on particle- and tip-enhanced Raman spectroscopic measurements of benzotriazole molecules adsorbed on gold films are presented.
Dawei Liang - One of the best experts on this subject based on the ideXlab platform.
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a path to renewable mg reduction from mgo by a continuous wave cr nd yag ceramic solar laser
Solar Energy Materials and Solar Cells, 2016Co-Authors: Mariana Oliveira, Dawei Liang, Joana Almeida, Claudia R Vistas, Filipe Goncalves, Rodrigo MartinsAbstract:Abstract The first successful ablation of magnesium oxide through a home-made continuous-wave Cr:Nd:YAG ceramic solar laser is reported. A stationary heliostat-Parabolic Mirror solar energy collection and concentration system was used. A stable continuous-wave laser output power of 19.2 W was attained with laser beam brightness figure of merit 7.6 times higher than that of the previous scheme, enabling therefore the direct ablation of pure magnesium by our solar-pumped laser with only 1.6 m 2 effective collection area. This could be an important step towards renewable magnesium production, offering multiple advantages, such as reducing agent avoidance, in relation to that of the previous Fresnel lens Cr:Nd:YAG continuous-wave solar laser system.
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5 5 w continuous wave tem 00 mode nd yag solar laser by a light guide 2v shaped pump cavity
Applied Physics B, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, R Bouadjemine, Emmanuel GuillotAbstract:A significant progress in TEM00-mode solar laser power and efficiency with heliostat–Parabolic Mirror system is reported here. A double-stage light-guide/2V-shaped pump cavity is used to efficiently couple and redistribute the concentrated pump light from a 2-m-diameter Parabolic Mirror to a 4-mm-diameter, 30-mm-length, 1.1 at.% Nd:YAG single-crystal rod. The light guide with large rectangular cross section enables a stable uniform pumping profile along the laser rod, resulting also in an enhanced tracking error compensation capacity. 5.5 W cw TEM00-mode solar laser power was measured at the output of a thermally near unstable asymmetric resonator. 150 and 157 % improvement in TEM00-mode solar laser collection efficiency and slope efficiency were obtained, respectively.
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56 w cw nd yag solar laser by a heliostat Parabolic Mirror system
European Quantum Electronics Conference, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, Emmanuel GuillotAbstract:Solar-pumped lasers are natural candidates for applications where sunlight is plentiful and few other energy sources are available. Since the first report of “A sun-pumped cw one-watt laser” in 1966 [1], optical and laser material advances have continued to improve solar laser performance. Parabolic Mirrors have long been explored to achieve tight focusing of incoming solar radiation. However, their use for solar laser researches has been neglected in recent years due to the increased interests in large-size Fresnel lenses. Fresnel lens is cost-effective, but it causes the dispersion of the solar radiation along its focal zone, hampering the efficient light concentration to the laser rod. It is therefore valuable for us to carry out the solar laser research with Parabolic Mirrors. A new progress in both solar laser collection efficiency and slope efficiency with heliostat - Parabolic Mirror system is reported here.
-
highly efficient end side pumped nd yag solar laser by a heliostat Parabolic Mirror system
Applied Optics, 2015Co-Authors: Joana Almeida, Dawei Liang, Claudia R Vistas, Emmanuel GuillotAbstract:We report a large improvement in the collection and slope efficiency of an Nd:YAG solar laser pumped by a heliostat–Parabolic Mirror system. A conical fused silica lens was used to further concentrate the solar radiation from the focal zone of a 2 m diameter primary concentrator to a Nd:YAG single-crystal rod within a conical pump cavity, which enabled multipass pumping to the active medium. A 56 W cw laser power was measured, corresponding to 21.1 W/m2 record-high solar laser collection efficiency with the heliostat–Parabolic Mirror system. 4.9% slope efficiency was calculated, corresponding to 175% enhancement over our previous result.
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solar pumped tem00 mode nd yag laser by a heliostat Parabolic Mirror system
Solar Energy Materials and Solar Cells, 2015Co-Authors: Dawei Liang, Joana Almeida, Claudia R Vistas, Emmanuel GuillotAbstract:Abstract Here we report a significant advance in solar-pumped laser beam brightness by pumping a 3 mm diameter Nd:YAG single-crystal rod with a heliostat-Parabolic Mirror system. The incoming solar radiation is first collected and focused by the system. A rectangular fused silica light guide and a 2D-CPC concentrator are then combined to further compress the concentrated solar radiation into the laser rod within a V-shaped pumping cavity. 4.4 W continuous-wave TEM 00 mode ( M 2 ≤1.05) 1064 nm solar laser power is finally produced, attaining 4.0 W laser beam brightness figure of merit, which is 2.1 times higher than the previous record by a Fresnel lens. 0.81% TEM 00 mode laser slope efficiency is achieved.
