Search results for "two-photon [exchange]"
showing 6 items of 56 documents
The correlation of the 7.6 eV optical absorption band in pure fused silicon dioxide with twofold-coordinated silicon
1992
Abstract The optical absorption band at 7.6 eV, which appears in oxygen deficient pure silica, does not correlate with any ESR signal in non-irradiated samples. Longlasting illumination at 80 K in the range of its absorption leads to an increase of the absorption band at 5 eV. Subsequent heating to 290 K restores the initial absorption. These data can be explained as photodissociation and thermal recreation of a complex defect containing a twofold-coordinated silicon defect. This complex defect is responsible for the 7.6 eV absorption band.
Dispersion management in two-photon microscopy by using diffractive optical elements.
2013
We demonstrate efficient generation of wide-field fluorescence signals in two-photon microscopy exploiting diffractive optical elements and short pulses by using a dispersion-compensated beam delivery optics module. Computer-generated holograms are codified onto a phase-only spatial light modulator, which allows for arbitrary single-shot patterning of the sample. Spatiotemporal shaping of the pulse is mandatory to overcome spatial chirp and pulse-front tilt effects that spread both in space and time the irradiance patterns, thus limiting not only the spatial resolution but also the signal-to-noise ratio in two-photon microscopy. By using a multipass amplifier delivering 30 fs, 0.8 mJ pulses…
Determination of Kerr and two-photon absorption coefficients of indandione derivatives
2017
This material is based upon work supported by the ERDF 1.1.1.1 activity project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices” as well as by National Research Program “Multifunctional Materials and Composites, Photonics and Nanotechnology” (IMIS2) project “Photonics and materials for photonics”.
On the Schwarzschild Effect in 3D Two‐Photon Laser Lithography
2019
International audience; The two‐photon Schwarzschild effect in photoresists suitable for 3D laser lithography is revisited. The study ranges over seven orders of magnitude in exposure time (from 1 µs to 10 s) and investigates a wide variety of different photoresist compositions. For short exposure times (“regime I”), the laser power at the polymerization threshold can scale with the inverse square root of the exposure time, as naively to be expected for two‐photon absorption. Substantial deviations occur, however, for low photoinitiator concentrations. For intermediate exposure times (“regime II”), a Schwarzschild‐type of behavior is found, as discussed previously. For very long exposure ti…
Synthesis and photophysical properties of hyperbranhced polyfluorenes containing 2,4,6-tris(tiophen-2-yl)-1,3,5-triazine as the core
2011
A series of new hyperbranched polymers containing a 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine core unit and polyfluorene chain arms have been synthesized via Suzuki coupling, and characterized by NMR, IR and GPC. All the polymers exhibit good thermal stability with a high decomposition temperature. By changing the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine/fluorene ratio the UV-vis absorption and emission spectra can be partially tuned. It has been found that the polymers containing a low ratio of 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine units (P1-P3) have an absorption maximum around 385 nm, localized in the polyfluorene chain, and a shoulder around 425 nm ascribable to a charge transfer stat…
Two-photon excitation microscopy of tryptophan-containing proteins.
2002
We have examined the feasibility of observing single protein molecules by means of their intrinsic tryptophan emission after two-photon excitation. A respiratory protein from spiders, the 24-meric hemocyanin, containing 148 tryptophans, was studied in its native state under almost in vivo conditions. In this specific case, the intensity of the tryptophan emission signals the oxygen load, allowing one to investigate molecular cooperativity. As a system with even higher tryptophan content, we also investigated latex spheres covered with the protein avidin, resulting in 340 tryptophans per sphere. The ratio of the fluorescence quantum efficiency to the bleaching efficiency was found to vary b…