Bahlmann, Karsten

[["dc.bibliographiccitation.firstpage","RP1"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","J. Microsc."],["dc.bibliographiccitation.lastpage","RP2"],["dc.bibliographiccitation.volume","180"],["dc.contributor.author","Hell, S. W."],["dc.contributor.author","Schrader, M."],["dc.contributor.author","Bahlmann, K."],["dc.contributor.author","Meinecke, F."],["dc.contributor.author","Lakowicz, J. R ."],["dc.contributor.author","Gryczynski, I."],["dc.date.accessioned","2018-03-21T14:33:54Z"],["dc.date.available","2018-03-21T14:33:54Z"],["dc.date.issued","1995"],["dc.description.abstract","We report the realization of stimulated emission on a microscopic scale. An experiment is presented describing significant depopulation of the excited state of the fluorophore Pyridine 2 with a mode‐locked Ti: Sapphire laser. Stimulated emission is performed at 750 nm and excitation at the frequency doubled wavelength of 375 nm. The pulses are synchronized so that the stimulating pulse follows the excitation pulse after 5 ps. The set‐up is a modified 4Pi‐confocal microscope employing one of the objective lenses for excitation and the opposing one for stimulated emission."],["dc.identifier.doi","10.1111/j.1365-2818.1995.tb03662.x"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/13111"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.status","final"],["dc.title","Stimulated Emission on a Microscopic Scale: Light Quenching of Pyridinium 2 using a Ti:Sapphire laser"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1652"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Applied Optics"],["dc.bibliographiccitation.lastpage","1658"],["dc.bibliographiccitation.volume","39"],["dc.contributor.author","Bahlmann, Karsten"],["dc.contributor.author","Hell, Stefan W."],["dc.date.accessioned","2017-09-07T11:47:22Z"],["dc.date.available","2017-09-07T11:47:22Z"],["dc.date.issued","2000"],["dc.description.abstract","We studied the effect of electric field orientation on the point-spread function (PSF) of a 4Pi microscope. We show that in a standard 4Pi arrangement the orientation of the field can be used for changing between constructive- and destructive-mode 4Pi microscopy. The effect is counteracted by introduction of a phase shift of a into one of the half-arms. This compensation is compulsory during illumination with unpolarized or circularly polarized light. By performing our experiments with 1.2-N.A, water-immersion lenses, we demonstrate that water immersion is suitable for 4Pi confocal microscopy. At a two-photon excitation wavelength of 1064 nm, the water 4Pi confocal PSF features an axial lobe of 40% above and below the focal plane, which, by linear filtering, can be unambiguously removed. The measured axial full width at half-maximum of the PSF is 240 nm. This is 4.3 times narrower than its single-lens confocal counterpart. The 4Pi confocal microscope sets a new resolution benchmark in three-dimensional imaging of watery samples."],["dc.identifier.doi","10.1364/AO.39.001652"],["dc.identifier.gro","3144401"],["dc.identifier.isi","000086210900029"],["dc.identifier.pmid","18345065"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/2021"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.eissn","2155-3165"],["dc.relation.issn","1559-128X"],["dc.title","Polarization effects in 4Pi confocal microscopy studied with water-immersion lenses"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","147"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Bioimaging"],["dc.bibliographiccitation.lastpage","153"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Schrader, Martin"],["dc.contributor.author","Meinecke, Franziska"],["dc.contributor.author","Bahlmann, Karsten"],["dc.contributor.author","Kroug, Matthias"],["dc.contributor.author","Cremer, Christoph"],["dc.contributor.author","Soini, Erkki"],["dc.contributor.author","Hell, Stefan W."],["dc.date.accessioned","2018-03-21T15:33:04Z"],["dc.date.available","2018-03-21T15:33:04Z"],["dc.date.issued","1995"],["dc.description.abstract","A two‐pulse experiment is described, using stimulated emission to reduce the fluorescence of 1‐ethyl‐4‐(4‐(p‐dimethylaminophenyl)‐1,3‐butadienyl)‐pyridinium perchlorate (Pyridine 2) in a microscope of high numerical aperture. The experiment employed a 130 fs pulse at 375 nm for excitation and a 20 ± 5 ps pulse at 750 nm for stimulated emission. The pulses were provided by a mode‐locked Ti:sapphire laser. The 375 nm excitation pulse was obtained by frequency‐doubling and the 20 ± 5 ps infrared pulse by optical grating dispersion. The population of the excited state was monitored by varying the temporal delay between the excitation and stimulating pulse. This method enabled the measurement of the lifetime of the dye. For Pyridine 2 in glycerol, we determined a lifetime of 0.86 ± 0.2 ns. The decrease of fluorescence was due to stimulated emission, as was established by measurements of the temporal behaviour of the fluorescence signal upon amplitude modulation of the stimulating beam. We present a theoretical analysis of the temporal behaviour of depletion by stimulated emission in a two‐pulse experiment."],["dc.identifier.doi","10.1002/1361-6374(199512)3:4<147::AID-BIO1>3.0.CO;2-H"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/13115"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.title","Monitoring the excited state of a fluorophore in a microscope by stimulated emission"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","155"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Ultramicroscopy"],["dc.bibliographiccitation.lastpage","164"],["dc.bibliographiccitation.volume","87"],["dc.contributor.author","Bahlmann, Karsten"],["dc.contributor.author","Jakobs, Stefan"],["dc.contributor.author","Hell, Stefan W."],["dc.date.accessioned","2017-09-07T11:46:39Z"],["dc.date.available","2017-09-07T11:46:39Z"],["dc.date.issued","2001"],["dc.description.abstract","By coherently adding the spherical wavefronts of two opposing lenses, two-photon excitation 4Pi-confocal fluorescence microscopy has achieved three-dimensional imaging with an axial resolution 3-7 times better than confocal microscopy. So far this improvement was possible only in glycerol-mounted, fixed cells. Here we report 4Pi-confocal microscopy of watery objects and its application to the imaging of live cells. Water immersion of 4Pi-confocal microscopy of membrane stained live Escherichia coli bacteria attains a 4.3-fold better axial resolution as compared to the best water immersion confocal microscope. The resolution enhancement results into a vastly improved three-dimensional representation of the bacteria. The first images of live biological samples with an all-directional resolution in the 190-280 nm range are presented here, thus establishing a new resolution benchmark in live-cell microscopy."],["dc.identifier.doi","10.1016/S0304-3991(00)00092-9"],["dc.identifier.gro","3144294"],["dc.identifier.isi","000169316300006"],["dc.identifier.pmid","11330502"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1903"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0304-3991"],["dc.title","4Pi-confocal microscopy of live cells"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","59"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Journal of Microscopy"],["dc.bibliographiccitation.lastpage","67"],["dc.bibliographiccitation.volume","200"],["dc.contributor.author","Bahlmann, K."],["dc.contributor.author","Hell, S. W."],["dc.date.accessioned","2017-09-07T11:46:45Z"],["dc.date.available","2017-09-07T11:46:45Z"],["dc.date.issued","2000"],["dc.description.abstract","Electromagnetic focusing theory of light predicts that at high apertures field components arise that are polarized perpendicular to the initial polarization. Although vectorial depolarization has received considerable attention in focusing theory, no evidence has been presented as to its relevance in experiments. We measure the intensity of the perpendicularly orientated field in the focal region by utilizing monomolecular, fluorescent polydiacetylene layers whose transition dipoles are orientated in a single direction. For a 1.4 numerical aperture oil objective lens illuminated with linearly x-polarized light, we find that the integral of the modulus squared of the y-polarized focal field amounts to 1.5% of its x-polarized counterpart. In particular, we show here that the depolarization increases when using annular apertures. Annuli formed by a central obstruction with a diameter of 89% of that of the entrance pupil raise the integral to 5.5%. This compares well with the value of 5.8% predicted by electromagnetic focusing theory; however, the depolarization is also due to imperfections connected with focusing by refraction. Besides fluorescence microscopy and single molecule spectroscopy, the measured intensity of the depolarized component in the focal plane is relevant to all forms of light spectroscopy combining strong focusing with polarization analysis."],["dc.identifier.doi","10.1046/j.1365-2818.2000.00739.x"],["dc.identifier.gro","3144352"],["dc.identifier.isi","000089992400007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1966"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0022-2720"],["dc.title","Electric field depolarization in high aperture focusing with emphasis on annular apertures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","116"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Optik"],["dc.bibliographiccitation.lastpage","124"],["dc.bibliographiccitation.volume","104"],["dc.contributor.author","Schrader, M."],["dc.contributor.author","Bahlmann, K."],["dc.contributor.author","Hell, S. W."],["dc.date.accessioned","2017-09-07T11:51:04Z"],["dc.date.available","2017-09-07T11:51:04Z"],["dc.date.issued","1997"],["dc.description.abstract","We derive the three-dimensional resolution of three-photon excitation fluorescence microscopy and compare it with its single and two-photon excitation counterpart. We perform three-photon excitation microscopy in the 900-970 nm range and compare the experimentally determined axial resolution with that of two-photon excitation microscopy at the same excitation wavelength. At an excitation wavelength of 900 nm, we measure a resolution increase of 35% of three-photon over two-photon excitation microscopy. This is in good agreement with the theoretically predicted resolution increase. At 900 nm and an aperture of 1.4 oil immersion we obtain an axial resolution of 587 +/- 27 nm. Three-photon images are displayed of DAPI-labelled metaphase chromosomes. The images are recorded by using a train of subpicosecond pulses of a mode-locked Titanium-Sapphire laser emitting at a wavelength of 970 nm. We also discuss the role of the pulse length and that of point out the implications of three-photon excitation for other far-field fluorescence microscopies. Our findings also reveal the potential of superresolution for increasing the information density in three-photon induced three-dimensional data storage."],["dc.identifier.gro","3144624"],["dc.identifier.isi","A1997WG26800006"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/2269"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0030-4026"],["dc.title","Three-photon-excitation microscopy: Theory, experiment and applications"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","RP1"],["dc.bibliographiccitation.journal","Journal of microscopy"],["dc.bibliographiccitation.lastpage","RP2"],["dc.bibliographiccitation.volume","180"],["dc.contributor.author","Hell, Stefan"],["dc.contributor.author","Schrader, M."],["dc.contributor.author","Bahlmann, K."],["dc.contributor.author","MEINECKE, F"],["dc.contributor.author","Lakowicz, J. R ."],["dc.contributor.author","Gryczynski, I."],["dc.date.accessioned","2017-09-07T11:51:11Z"],["dc.date.available","2017-09-07T11:51:11Z"],["dc.date.issued","1995"],["dc.description.abstract","We report the realization of stimulated emission on a microscopic scale. An experiment is presented describing significant depopulation of the excited state of the fluorophore Pyridine 2 with a mode-locked Ti:Sapphire laser, Stimulated emission is performed at 750 nm and excitation at the frequency doubled wavelength of 375 nm. The pulses are synchronized so that the stimulating pulse follows the excitation pulse after 5 ps. The set-up is a modified 4Pi-confocal microscope employing one of the objective lenses for excitation and the opposing one for stimulated emission."],["dc.identifier.gro","3144674"],["dc.identifier.isi","A1995TJ43100015"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/2324"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0022-2720"],["dc.title","STIMULATED-EMISSION ON MICROSCOPIC SCALE - LIGHT QUENCHING OF PYRIDINE-2 USING A TI-SAPPHIRE LASER"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","612"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Applied Physics Letters"],["dc.bibliographiccitation.lastpage","614"],["dc.bibliographiccitation.volume","77"],["dc.contributor.author","Bahlmann, K."],["dc.contributor.author","Hell, S. W."],["dc.date.accessioned","2017-09-07T11:46:48Z"],["dc.date.available","2017-09-07T11:46:48Z"],["dc.date.issued","2000"],["dc.description.abstract","Wr introduce a method employing ferroelectric monomolecular layers, by which it is possible to measure the light field polarization in the focus of a lens. This method allowed us to noninvasively establish the perpendicularly oriented focal field that is anticipated at high apertures. For a numerical aperture 1.4 oil immersion lens illuminated with linearly polarized plane waves, the integral of the modulus square of the perpendicular component amounts to (1.51 +/- 0.2) % of that of the initial polarization. It is proven that depolarization decreases with decreasing aperture angle. Whereas for regular imaging conditions depolarization is largely negligible, it plays a significant role in microscopy of highest resolution, microspectroscopy, and single molecule studies."],["dc.identifier.doi","10.1063/1.127061"],["dc.identifier.gro","3144368"],["dc.identifier.isi","000088580300002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1984"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0003-6951"],["dc.title","Depolarization by high aperture focusing"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","71"],["dc.bibliographiccitation.journal","J. Biomed. Opt."],["dc.bibliographiccitation.lastpage","74"],["dc.bibliographiccitation.volume","1"],["dc.contributor.author","Hell, S. W."],["dc.contributor.author","Bahlmann, K."],["dc.date.accessioned","2018-03-20T12:24:55Z"],["dc.date.available","2018-03-20T12:24:55Z"],["dc.date.issued","1996"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/13098"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.title","Three-photon excitation in fluorescence microscopy"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1659"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Biophysical Journal"],["dc.bibliographiccitation.lastpage","1668"],["dc.bibliographiccitation.volume","75"],["dc.contributor.author","Schrader, Martin"],["dc.contributor.author","Bahlmann, Karsten"],["dc.contributor.author","Giese, Günter"],["dc.contributor.author","Hell, Stefan W."],["dc.date.accessioned","2022-03-01T11:45:27Z"],["dc.date.available","2022-03-01T11:45:27Z"],["dc.date.issued","1998"],["dc.description.abstract","By combining the wavefronts produced by two high-aperture lenses, two-photon 4Pi-confocal microscopy allows three-dimensional imaging of transparent biological specimens with axial resolution in the 100-140-nm range. We reveal the imaging properties of a two-photon 4Pi-confocal microscope as applied to a fixed cell. We demonstrate that a fast, linear point deconvolution suffices to achieve axially superresolved 3D images in the cytoskeleton. Furthermore, we describe stringent algorithms for alignment and control of the two lenses. We also show how to compensate for the effects of a potential refractive index mismatch of the mounting medium with respect to the immersion system."],["dc.identifier.doi","10.1016/S0006-3495(98)77608-8"],["dc.identifier.gro","3142373"],["dc.identifier.isi","000076144000006"],["dc.identifier.pii","S0006349598776088"],["dc.identifier.pmid","9746508"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/103333"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-531"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0006-3495"],["dc.title","4Pi-Confocal Imaging in Fixed Biological Specimens"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dc.type.subtype","original"],["dspace.entity.type","Publication"]]