Stimulated Emission

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Stefan W Hell - One of the best experts on this subject based on the ideXlab platform.

  • spectroscopic rationale for efficient Stimulated Emission depletion microscopy fluorophores
    Journal of the American Chemical Society, 2010
    Co-Authors: Junichi Hotta, Stefan W Hell, Eduard Fron, Peter Dedecker, Kris P F Janssen, Klaus Mullen, Benjamin Harke, Johanna Buckers, Johan Hofkens
    Abstract:

    We report a rationale for identifying superior dyes for Stimulated-Emission depletion (STED) microscopy. We compared the dyes pPDI and pTDI, which displayed excellent photostability in single-molecule spectroscopy. Surprisingly, their photostability and performance in STED microscopy differed significantly. While single pTDI molecules could be visualized with excellent resolution (35 nm), pPDI molecules bleached rapidly under similar conditions. Femtosecond transient absorption measurements proved that the overlap between the Stimulated-Emission band and the excited-state absorption band is the main reason for the observed difference. Thus, assessment of the excited-state absorption band provides a rational means of dye selection and determination of the optimal wavelength for STED.

  • Stimulated Emission depletion nanoscopy of living cells using snap tag fusion proteins
    Biophysical Journal, 2010
    Co-Authors: Birka Hein, Stefan Jakobs, Volker Westphal, Katrin I Willig, Christian A Wurm, Stefan W Hell
    Abstract:

    We show far-field fluorescence nanoscopy of different structural elements labeled with an organic dye within living mammalian cells. The diffraction barrier limiting far-field light microscopy is outperformed by using Stimulated Emission depletion. We used the tagging protein hAGT (SNAP-tag), which covalently binds benzylguanine-substituted organic dyes, for labeling. Tetramethylrhodamine was used to image the cytoskeleton (vimentin and microtubule-associated protein 2) as well as structures located at the cell membrane (caveolin and connexin-43) with a resolution down to 40 nm. Comparison with structures labeled with the yellow fluorescent protein Citrine validates this labeling approach. Nanoscopic movies showing the movement of connexin-43 clusters across the cell membrane evidence the capability of this technique to observe structural changes on the nanoscale over time. Pulsed or continuous-wave lasers for excitation and Stimulated Emission depletion yield images of similar resolution in living cells. Hence fusion proteins that bind modified organic dyes expand widely the application range of far-field fluorescence nanoscopy of living cells.

  • immunofluorescence Stimulated Emission depletion microscopy
    Nature Biotechnology, 2003
    Co-Authors: Marcus Dyba, Stefan Jakobs, Stefan W Hell
    Abstract:

    We report immunofluorescence imaging with a spatial resolution well beyond the diffraction limit. An axial resolution of approximately 50 nm, corresponding to 1/16 of the irradiation wavelength of 793 nm, is achieved by Stimulated Emission depletion through opposing lenses. We have demonstrated not only that an antibody-tagged label is stable enough to be recorded in this microscopy mode, but also that subdiffraction resolution can be obtained using a standard immunofluorescence preparation.

  • laser diode Stimulated Emission depletion microscopy
    Applied Physics Letters, 2003
    Co-Authors: Volker Westphal, Marcus Dyba, Carlo Mar Blanca, Lars Kastrup, Stefan W Hell
    Abstract:

    We report subdiffraction resolution in far-field fluorescence microscopy through laser-diode-Stimulated Emission depletion of molecular markers. The diode-generated focal intensities lead to a resolution improvement by ∼45% in both lateral directions. Excitation and Stimulated Emission are performed with electronically synchronized diode pulses of 50–70 ps and 300–400 ps duration, respectively. The subdiffraction resolution is utilized to resolve neighboring individual molecules.

  • fluorescence microscopy with diffraction resolution barrier broken by Stimulated Emission
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Thomas A Klar, Stefan Jakobs, Marcus Dyba, Alexander Egner, Stefan W Hell
    Abstract:

    The diffraction barrier responsible for a finite focal spot size and limited resolution in far-field fluorescence microscopy has been fundamentally broken. This is accomplished by quenching excited organic molecules at the rim of the focal spot through Stimulated Emission. Along the optic axis, the spot size was reduced by up to 6 times beyond the diffraction barrier. The simultaneous 2-fold improvement in the radial direction rendered a nearly spherical fluorescence spot with a diameter of 90–110 nm. The spot volume of down to 0.67 attoliters is 18 times smaller than that of confocal microscopy, thus making our results also relevant to three-dimensional photochemistry and single molecule spectroscopy. Images of live cells reveal greater details.

Asif M Khan - One of the best experts on this subject based on the ideXlab platform.

  • quantum shift of band edge Stimulated Emission in ingan gan multiple quantum well light emitting diodes
    Applied Physics Letters, 1997
    Co-Authors: C J Sun, Asif M Khan, Zubair M Anwar, Q Chen, J Yang, M S Shur, A D Bykhovski, Z Lilientalweber, C Kisielowski, M Smith
    Abstract:

    We report on the band-edge Stimulated Emission in InGaN–GaN multiple quantum well light-emitting diodes with varying widths and barrier thicknesses of the quantum wells. In these devices, we observe that the Stimulated Emission peak wavelength shifts to shorter values with decreasing well thickness. From the comparison of the results of the quantum mechanical calculations of the subbands energies with the measured data, we estimate the effective conduction- and valence-band discontinuities at the GaN–In0.13Ga0.87N heterointerface to be approximately 130–155 and 245–220 meV, respectively. We also discuss the effect of stress on the estimated values of band discontinuities.

  • vertical cavity Stimulated Emission from photopumped ingan gan heterojunctions at room temperature
    Applied Physics Letters, 1994
    Co-Authors: Asif M Khan, D T Olson, J N Kuznia, S Krishnankutty, Richard A Skogman, T George
    Abstract:

    We report the observation of room temperature violet (415 nm) Stimulated Emission in the vertical cavity mode from photopumped GaN/In0.25Ga0.75N heterojunctions. The InGaN/GaN heterojunction was deposited over sapphire substrates using low‐pressure metalorganic chemical vapor deposition and was of high enough optical quality to achieve room‐temperature Stimulated Emission. The observed Emission intensity was found to be a nonlinear function of incident optical pump power density. At threshold we observe a clear line narrowing of the output optical signal from 20 to 1.5 nm full width at half‐maximum.

  • vertical cavity room temperature Stimulated Emission from photopumped gan films deposited over sapphire substrates using low pressure metalorganic chemical vapor deposition
    Applied Physics Letters, 1991
    Co-Authors: Asif M Khan, D T Olson, J M Van Hove, J N Kuznia
    Abstract:

    We report the first observation of near‐UV vertical‐cavity Stimulated Emission from a photopumped GaN epilayer at room temperature. The epilayer was deposited over AIN‐coated basal plane sapphire substrate using low‐pressure metalorganic chemical vapor deposition. Epitaxy quality of a 1.5‐μm‐thick GaN layer was high enough to achieve Stimulated Emission at room temperature. The observed near‐UV optical Emission power was a nonlinear function of the pump power density. At threshold power density, we also observed line narrowing and a shift of the peak UV Emission towards longer wavelengths. Data comparing the UV Emission for the vertical‐cavity and the edge Emission geometry are also presented.

Marlan O Scully - One of the best experts on this subject based on the ideXlab platform.

Mark I Stockman - One of the best experts on this subject based on the ideXlab platform.

David J Bergman - One of the best experts on this subject based on the ideXlab platform.