Laurent Sarger

Optical non-linearity in oxide glasses

The origin of the optical non-linear response has been investigated in two different types of oxide glasses. Linear and non-linear refractive indices have been obtained by interferometric measurements. Correlations between the local structure of polarizable entities within glasses and their optical activities have been tentatively established through ab initio calculations.

Optical properties of infrared femtosecond laser-modified fused silica and application to waveguide fabrication

We investigate the changes in the optical properties of fused silica exposed to intense infrared femtosecond pulses. The laser-induced absorption spectrum reveals the creation of color centers inside the glass matrix, comparable with those observed in ultraviolet-exposed fused silica. The laser-induced absorption is associated with a laser-induced refractive-index change, which can be used for waveguide fabrication. The change in third-order susceptibility in such waveguides is measured by third-harmonic-generation microscopy as a function of the irradiation parameters.

Precise and absolute measurements of the complex third-order optical susceptibility

We present precise and absolute measurements of full complex third-order optical susceptibility on different fused-silica and original glasses composed of tellurium, titanium, and niobium erbium. These materials are designed to be the key point for applications ranging from high-power laser systems to optoelectronics; their nonlinear index of refraction is a major property and thus must be accurately known. A large dispersion (more than 30%) of the nonlinear index of fused-silica glasses was found. Measurements on tellurium glasses have shown strong nonlinearities, to be linked to the configurations of their cations and anions.

Study of a Linear Femtosecond Laser in Passive and Hybrid Operation

Astigmatism compensation and stability of a linear mode-locked femtosecond dye laser is analysed. Hybrid and passive mode-locking operation of the astigmatic compensated cavity is discussed. A direct study of the colliding pulse effect is made.

High power, continuous-wave ytterbium-doped fiber laser tunable from 976 to 1120 nm.

We report on a linearly-polarized, continuous-wave Ytterbium-doped fiber laser continuously tunable on the fly over an unprecedented emission bandwidth ranging from 976 nm to 1120 nm and delivering a minimum of 10 W and a maximum of 41 W. Additionally, the bandwidth of the system can be tuned from 100 pm to more than 1 nm at all wavelengths.

Nonlinear optical properties for TiO2 containing phosphate, borophosphate, and silicate glasses

A theoretical and experimental analysis of the optical properties for titanium-containing glasses is reported. A bond orbital theory elaborated by M. E. Lines [Phys. Rev. B 41, 3372 (1990); 41, 3383 (1990); 43, 11 978 (1991)] for crystals has been extended to these glasses, where the influence of the Ti–O bond environment has been considered. The resulting calculated values obtained for linear and nonlinear indices have been successfully compared with absolute experimental indices independently measured using a Mach–Zehnder interferometer. This agreement involves an adjustment of a local field factor f, varying from 1 to 1.2, which emphasizes the importance of the titanium–oxygen environment particularly upon the nonlinear optical properties of the investigated materials.

Thermally poled new borate glasses for second harmonic generation

Abstract Second harmonic generation (SHG) in poled glasses opens new opportunities in material research and device development for optics. Within this context (1−x)LaMgB5O10–xTiO2 and (1−x) LaMgB 5 O 10 –x Nb 2 O 5 (0⩽x⩽0.4) glasses have been formed and characterized. The structure of unpoled glasses has been studied by IR, Raman, and XAFS spectroscopies. Optical properties of transmission like linear refractive indexes and third-order non-linear optical susceptibility χ(3) have been investigated. A second harmonic signal was observed for each thermally poled composition, except for the LaMgB5O10 matrix glass.

Precise measurements and analysis of linear and nonlinear optical properties of glass materials near 1.5 μm

Abstract We adapted a time resolved Mach–Zehnder interferometric technique using a synchronously pumped optical parametric oscillator to measure accurate and absolute nonlinear χ3 in the IR telecommunications domain. Results have been obtained for various metal oxide glasses. Taking into account measurements done at different wavelengths using the same set-up, dispersion of electronic nonlinearity has been studied. Thermal properties have also been measured and very low absorption coefficients of these materials have been analyzed.

Complete pulse characterization: measurements of linear and nonlinear properties

We present a frequency-domain phase measurement technique coupled with a numerical chirp processing of the recorded sonogram to realise a pulse characterisation. Applications to the propagation of ultrashort pulses in linear and nonlinear media are investigated. Calibration of the experimental setup is performed using spectral interferometry technique. Results on linear dispersion glass and Kerr effect in vitreous samples are presented.

XANES and EXAFS study of glasses of the TiO2Na2OP2O5 system

Abstract X-ray absorption measurements (XANES-EXAFS) have been performed on the series of glasses with composition x TiO 2 ·y Na 2 O ·z P 2 O 5 (y/z = 4 3 and x = 10.7 mol %) . Two TiO distances of about 1.65 A and 1.95 A have been found, and TiTi correlations (about 3.4 A) have been observed for x = 26.4 and 34.6%. A model is proposed to explain the progressive modifications of XANES and EXAFS spectra with increasing x. Two different types of site for titanium have been identified in these glasses, in which Ti is respectively sixfold- and fivefold-coordinated. The rate of fivefold-coordinated Ti increases with increasing x.