Alain Brun

Photostability of dye molecules trapped in solid matrices

The photostability of dye molecules trapped in transparent solid matrices synthesized by the solgel technique was studied both experimentally and theoretically using a model with numerical and approximate analytical solutions. The model is based on a one-photon photodestruction process with the creation of an absorbing bleached molecule. We give the number of photons that different trapped dye molecules can absorb on average before they are bleached. Dyes such as Perylene Red, Perylene Orange, Pyrromethenes 567 and 597, Rhodamines 6G and B, DCM, a Xanthylium salt, and Neon Red were investigated; significant differences were observed. Some dye molecules in solvents were also studied; increased stability resulted when the molecules were trapped in solid matrices.

Single-shot measurement of a 52-fs pulse

We demonstrate the possibility of a 52-fs pulse single-shot measurement by using the spatial analysis of the second harmonic beam produced in an optical autocorrelator. We show that this method gives means of optimizing low repetition rate femtosecond amplifiers.

Toward millions of laser pulses with pyrromethene- and perylene-doped xerogels

Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By using longitudinal pumping with a frequency-doubled Q-switched Nd: YAG laser, we obtained as much as 86% slope efficiency and 5 x 10(5) pulses lifetime. Furthermore, newly prepared deoxygenated samples exhibited even greater lifetimes.

Generation of 90-fs pulses from a mode-locked diode-pumped Yb 3+ :Ca 4 GdO(BO 3 ) 3 laser

A diode-pumped Yb>(3+):Ca(4)GdO(BO>(3))(3) (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MHz.

Efficient tunable solid-state laser near 630 nm using sulforhodamine 640-doped silica gel

Lasing is observed near 630 nm in a sulforhodamine 640-doped silica gel pumped by frequency-doubled radiation from a Q-switched Nd:YAG laser. A conversion efficiency of 20% is obtained. The laser wavelength is tunable over 40 nm.

Reverse saturable absorption in solid xerogel matrices

Aluminophthalocyanine (APC) and fullerene carbon 60 (C60) have been studied encaged in different silica matrices. The reverse saturable absorption properties of these doped xerogels have been compared to those of reference solutions of APC and C60. We show that reverse saturable absorber molecules retain their properties even when they are enclosed in the pores of a solid xerogel matrix.Aluminophthalocyanine (APC) and fullerene carbon 60 (C60) have been studied encaged in different silica matrices. The reverse saturable absorption properties of these doped xerogels have been compared to those of reference solutions of APC and C60. We show that reverse saturable absorber molecules retain their properties even when they are enclosed in the pores of a solid xerogel matrix.

Spectroscopic properties and laser performances of Yb:YCOB and potential of the Yb:LaCOB material

Abstract In order to increase the compacity of the Yb-doped lasers, YCOB (Ca 4 Y(BO 3 ) 3 ) materials with high ytterbium concentration have been characterized. Large 15 at.% and 35 at.% ytterbium-doped single crystals were grown by the Czochralski pulling method. Spectroscopic and laser properties have been investigated and laser tests performed under titanium sapphire and diode pumping at 976 nm. Low thresholds under Ti:Sa pumping (50 mW) and high slope efficiency under diode pumping (66%) have been obtained. The optical quality and the distribution of Yb 3+ dopant through the highly doped crystals is discussed. First results on the Yb:LaCOB crystals grown by the Czochralski process, containing 46Yb 3+ at.%, are also presented.

Theoretical and experimental investigations of a diode-pumped quasi-three-level laser: the Yb/sup 3+/-doped Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (Yb:GdCOB) laser

We present a theoretical and experimental analysis of a diode-pumped Yb/sup 3+/-doped Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (Yb:GdCOB) laser. A new model for a diode-pumped quasi-three-level laser is described. The effects of absorption saturation, temperature profile, and the beam quality M/sup 2/ factor of the pump diode have been taken into account, for the first time to our knowledge. We have obtained a good agreement between experimental measurements and theoretical calculations with two different pump wavelengths, 902 and 976 nm. Our model has given good predictions of the laser performances for different crystal temperatures and different M/sup 2/ factors of the pump beam. As much as 440 mW of output power (at 1082 nm) have been achieved for 640 mW of absorbed pump power at 976 nm, corresponding to one of the highest slope efficiencies (81%) ever obtained with Yb-doped lasers.

Observation and analysis of the fast photorefractive process in BSO

Abstract The dynamic behaviour of both diffracted beams in a two-wave mixing configuration, and induced photocurrent are investigated with nanosecond light excitation. The photorefractive Bi 12 SiO 20 (BSO) responds in the nanosecond time scale. The presence of thermally excited traps just under the conduction band must be considered. Attention should be paid to values for mobilities, lifetimes, etc. which characterize the material and could appear different from the values measured in experiments made with low power continuous laser beams.

Effect of chromophore–chromophore electrostatic interactions in the NLO response of functionalized organic–inorganic sol–gel materials ☆

Abstract In the last years, important non-linear optical (NLO) results on sol–gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push–pull chromophores either incorporated as guest in a high T g polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages, however they require significant improvement at the molecular level—by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore–chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their NLO properties. This has not been explored at all in sol–gel systems. In this work, the sol–gel route was used to prepare hybrid organic–inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole–dipole interactions through both: the tuning of the push–pull chromophore concentration and the control of tetraethoxysilane concentration, we have obtained a r 33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r 33 around 50 pm/V at 831 nm for a new optimized chromophore structure.