50 research outputs found
Broadly tunable (440-670 nm) solid-state organic laser with disposable capsules
An innovative concept of thin-film organic solid-state laser is proposed,
with diffraction-limited output and a broad tuning range covering the visible
spectrum under UV optical pumping. The laser beam is tunable over 230 nm, from
440 to 670 nm, with a 3 nm full width at half maximum typical spectral width.
The structure consists of a compact fixed bulk optical cavity, a polymeric
intracavity etalon for wavelength tuning, as well as five different disposable
glass slides coated with a dye-doped polymer film, forming a very simple and
low-cost gain medium. The use of interchangeable/disposable "gain capsules" is
an alternative solution to photodegradation issues, since gain chips can be
replaced without realignment of the cavity. The laser lifetime of a single chip
in ambient conditions and without encapsulation was extrapolated to be around
107 pulses at a microjoule energy-per-pulse level
White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting
Non-doped white organic light-emitting diodes using an ultrathin
yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on
either side of the interface between a hole-transporting NPB
(4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi
(4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the
thickness and the position of the rubrene layer allow fine chromaticity tuning
from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33,
y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of
70. Such a structure also provides an accurate sensing tool to measure the
exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively)
Comment on " Gain coefficient method for amplified spontaneous emission in thin waveguided film of a conjugated polymer " [APL 93, 163307 (2008)]
Comment on " Gain coefficient method for amplified spontaneous emission in
thin waveguided film of a conjugated polymer " [APL 93, 163307 (2008)
Highly-efficient, diffraction-limited laser emission from a Vertical External Cavity Surface-emitting Organic Laser
We report on a solid-state laser structure being the organic counterpart of
the Vertical External-Cavity Surface-Emitting Laser (VECSEL) design. The gain
medium is a poly (methyl methacrylate) film doped with Rhodamine 640,
spin-casted onto the High-Reflectivity mirror of a plano-concave resonator.
Upon pumping by 7-ns pulses at 532 nm, a diffraction-limited beam (M^2=1) was
obtained, with a conversion efficiency of 43%; higher peak powers (2kW) could
be attained when resorting to shorter (0.5 ns) pump pulses. The spectrum was
controlled by the thickness of the active layer playing the role of an
intracavity etalon; tunability is demonstrated over up to 20 nm
Tunable Ultraviolet Vertically-emitting Organic Laser
International audienceA solid-state organic thin-film laser with intracavity frequency doubling is reported. Tunable ultraviolet emission from 309 to 322 nm is achieved from a vertical external cavity surface-emitting organic laser, with 2 % efficiency (1 µJ at 315 nm). The laser comprises a polymethyl(methacrylate) layer doped with Rhodamine 640, spun-cast onto a plane mirror, a remote concave mirror, a nonlinear crystal and a dichroic separator. The output is spectrally narrow (<0.5 nm FWHM) and tunable through phase-matching selection of the fundamental radiation lasing modes. These results highlight a low-cost and portable alternative to tunable UV laser sources, useful for spectroscopic applications
Recent advances in solid-state organic lasers
Organic solid-state lasers are reviewed, with a special emphasis on works
published during the last decade. Referring originally to dyes in solid-state
polymeric matrices, organic lasers also include the rich family of organic
semiconductors, paced by the rapid development of organic light emitting
diodes. Organic lasers are broadly tunable coherent sources are potentially
compact, convenient and manufactured at low-costs. In this review, we describe
the basic photophysics of the materials used as gain media in organic lasers
with a specific look at the distinctive feature of dyes and semiconductors. We
also outline the laser architectures used in state-of-the-art organic lasers
and the performances of these devices with regard to output power, lifetime,
and beam quality. A survey of the recent trends in the field is given,
highlighting the latest developments in terms of wavelength coverage,
wavelength agility, efficiency and compactness, or towards integrated low-cost
sources, with a special focus on the great challenges remaining for achieving
direct electrical pumping. Finally, we discuss the very recent demonstration of
new kinds of organic lasers based on polaritons or surface plasmons, which open
new and very promising routes in the field of organic nanophotonics
Inkjet-printed vertically emitting solid-state organic lasers
In this paper, we show that Inkjet Printing can be successfully applied to
external-cavity vertically-emitting thin-film organic lasers, and can be used
to generate a diffraction-limited output beam with an output energy as high as
33.6 uJ with a slope efficiency S of 34%. Laser emission shows to be
continuously tunable from 570 to 670 nm using an intracavity polymer-based
Fabry-Perot etalon. High-optical quality films with several um thicknesses are
realized thanks to ink-jet printing. We introduce a new optical material where
EMD6415 commercial ink constitutes the optical host matrix and exhibits a
refractive index of 1.5 and an absorption coefficient of 0.66 cm-1 at 550-680
nm. Standard laser dyes like Pyromethene 597 and Rhodamine 640 are incorporated
in solution to the EMD6415 ink. Such large size " printed pixels " of 50 mm 2
present uniform and flat surfaces, with roughness measured as low as 1.5 nm in
different locations of a 50um x 50um AFM scan. Finally, as the gain capsules
fabricated by Inkjet printing are simple and do not incorporate any tuning or
cavity element, they are simple to make, have a negligible fabrication cost and
can be used as fully disposable items. This works opens the way towards the
fabrication of really low-cost tunable visible lasers with an affordable
technology that has the potential to be widely disseminated
Enhanced generation of VUV radiation by four-wave mixing in mercury using pulsed laser vaporization
The efficiency of a coherent VUV source at 125 nm, based on 2-photon resonant
four-wave mixing in mercury vapor, has been enhanced by up to 2 orders of
magnitude. This enhancement was obtained by locally heating a liquid Hg surface
with a pulsed excimer laser, resulting in a high density vapor plume in which
the nonlinear interaction occurred. Energies up to 5 μJ (1 kW peak power)
have been achieved while keeping the overall Hg cell at room temperature,
avoiding the use of a complex heat pipe. We have observed a strong saturation
of the VUV yield when peak power densities of the fundamental beams exceed the
GW/cm2 range, as well as a large intensity-dependant broadening (up to ~30
cm-1) of the two-photon resonance. The source has potential applications for
high resolution interference lithography and photochemistry
Etude des phénomènes de photodégradation et de polarisation dans les lasers organiques solides à cavité verticale externe
Although organic solid-state dye lasers can provide wavelenght tunability in the whole visible spectrum and offers perpectives of low-cost compact lasers, they are still limited by several drawbacks, especially photodegradation. The geometry of a Vertical External Cavity Surface-emitting Organic Laser (VECSOL) enables organic lasers to reach high energies, excellent conversion efficiences and good beam quality, it also enables an external control on many parameters, a feature that we have udes here to study the photodegradation phenomenon as well as some polarization properties of organic solid-state lasers. In the first part of this thesis, we studied the lifetime of the laser upon varying several parameters (pump pulsewidth, repetition rate, output coupling, ...) and we found that the intracavity laser intensity, independently of the pump intensity, had a major on photodegradation rate. Moreover, we observed that the profile of the laser beam was also degrading with time : while it is Gaussian in the beginning it gradually shifts to an annular shape. In the second part, we investigated the polarization properties of VECSOLs, with a special emphasis on fluorescence properties of some typical dyes used in lasers. The crucial role played by resonant nonradiative energy transfers between dye molecules (HOMO-FRET) is evidenced and enables explaining the observed fluorescence depolarization, compared to the expected limiting fluorescence anisotropy. Energy transfers happen to play a negligible role above laser threshold, as the organic laser beam is shown to be linearly polarized in a wide range of experimental conditions when excitation occurs in the first singlet state.Les lasers organiques solides disposent d’atouts considérables par rapport aux autres types de laser : l’accordabilité en longueur d’onde dans le visible et la simplicité de fabrication. Ils restent néanmoins à la marge d’une commercialisation et le phénomène de photodégradation en est la principale cause. Le VECSOL pour Vertical External Cavity Surface-emitting Organic Laser est une structure de laser particulièrement bien adaptée pour l’étudier car elle permet un contrôle très simple de plusieurs paramètres pouvant entrer en jeu dans le phénomène de photodégradation. Ainsi lors de cette thèse, où nous avons cherché à comprendre quels sont les facteurs ayant une influence sur la durée de vie des lasers, l’intensité intracavité s’est par exemple révélée être un élément crucial : plus elle est grande, plus la durée du laser est grande. Par ailleurs, un suivi en temps réel de la forme du faisceau laser a montré que celle-ci, gaussienne au départ, devenait annulaire avant de s’éteindre traduisant la « mort » progressive des molécules sollicitées pendant le pompage.Une seconde partie de la thèse concerne la polarisation de la fluorescence des molécules organiques utilisées en laser solide. Nous avons montré que la concentration en colorant influençait grandement la dépolarisation de l’émission spontanée. Enfin, en fonctionnement laser, le faisceau reste polarisé rectilignement (comme la pompe) quel que soit la concentration en colorant