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Papers by Stephane Santran

HAL (Le Centre pour la Communication Scientifique Directe), Nov 2, 2006

Through examining the product of the mathematical variance of intensity with respect to time and ... more Through examining the product of the mathematical variance of intensity with respect to time and frequency, we arrive at a temporal characterization of laser pulses through parameters for pulse duration, group delay dispersion and temporal form. These statistics, which are sufficient to predict subsequent pulse behavior, are recoverable in a simple experiment, measuring the two-photon-induced photocurrents in three nonlinear diodes. With only two photodiodes, we demonstrate that pulse durations as low as several tens of femtoseconds can be easily measured in a single shot if the usual assumptions of pulse form and dispersion are made as in the more difficult autocorrelation setup.

Proceedings of SPIE, Nov 29, 2000

ABSTRACT We present precise and absolute measurements of full complex third order optical suscept... more ABSTRACT We present precise and absolute measurements of full complex third order optical susceptibility on different fused silica and original glasses composed of tellurium, titanium, niobium erbium. These materials are designed to be the key point for applications ranging form high power laser systems to optoelectronics, their nonlinear index of refraction is a major property and thus must be accurately known. Due to the accuracy and sensitivity of our technique, we have been able to find a large dispersion (more than 30%) of the non linear index of fused silica glasses as a function of their processing mode. On the other hand, measurements on tellurium glasses have shown very strong nonlinearities (40 times higher than fused silica), to be linked to the configurations of their cations and anions. Although the titanium and niobium glasses are less nonlinear, they can be promising matrices for addition of luminescent entities like erbium leading to very interesting laser amplification materials. The experimental set-up is a collinear pump-probe (orthogonally polarized) experiment using transient absorption technique. It is built with around a 100 femtosecond laser oscillator. A fast oscillating delay between the pump and the probe allows us to measure the electronic nonlinearity in quasi real-time. This experiment has the following specifications: an absolute measurement accuracy below 10% mainly due to the laser parameters characterization, a relative measurement accuracy of 1% and a resolution less than 5.10-24m2/V2(50 times less than fused silica).

This invention relates to the field of tools determining the chemical composition of a sample.The... more This invention relates to the field of tools determining the chemical composition of a sample.The present invention relates more particularly to an improvement in the detection of chemical elements in a sample by fluorescence emission induced by a laser (LIF: laser Induced fluorescence) .It relates to a system for detecting at least one chemical element in a material comprising at least one laser emitting means to ionize a portion of said material to create a fluorescence, characterized in that it comprises at least one Bragg type of network transmission for filtering the wavelength corresponding to the excitation wavelength of the element and at least one photodiode for detecting the corresponding line said wavelength.

An autocorrelator-like set up is proposed to characterize optical nonlinear effects in a photodio... more An autocorrelator-like set up is proposed to characterize optical nonlinear effects in a photodiode. Experimental results are confronted with theoretical analysis at second and third orders, justifying two photon absorption use in auto-correlators.

Fourier Transform Spectroscopy/ Hyperspectral Imaging and Sounding of the Environment, 2007

ABSTRACT In the framework of spatial aperture synthesis, we developed a temporal aperture synthes... more ABSTRACT In the framework of spatial aperture synthesis, we developed a temporal aperture synthesis allowing the concatenation of several interferograms. We succeed to enhance the resolving power of static Fourier-transform spectrometers by a factor of 40.

2006 Northern Optics, 2006

By examining the first- and second-order moments of intensity with respect to time and frequency,... more By examining the first- and second-order moments of intensity with respect to time and frequency, we arrive at a temporal characterization of laser pulses through parameters for pulse duration, group delay dispersion and temporal form. These parameters, which are sufficient to predict subsequent pulse behavior, are recoverable in a simple experiment, measuring the two-photon-induced photocurrents in three nonlinear diodes. With only two photodiodes, we demonstrate that pulse durations as low as several tens of femtoseconds can be easily measured in a single shot, if the usual assumptions of pulse form and dispersion are made as in the more difficult autocorrelation setup.

Optical Materials, 2006

Nonlinear properties of a photo-thermo-refractive (PTR) glass are studied and compared with those... more Nonlinear properties of a photo-thermo-refractive (PTR) glass are studied and compared with those in fused silica and a conventional optical glass. PTR glass is a new photosensitive medium for high-efficiency phase volume hologram recording which manifests a linear refractive index modulation after exposure to UV radiation followed by thermal treatment. Nonlinear optical properties of PTR glass exposed to femtosecond laser pulses are studied. Diffraction patterns in a propagated laser beam focused in the sample were detected by a CCD, while a nonlinear refractive index was measured by a collinear-orthogonal-polarizationpump-probe (COP3) method. It was found that nonlinear refractive index of PTRG is n 2 = 3.3 • 10 À20 m 2 /W (0.33 ppm cm 2 / GW) which is about the same as for the fused silica. It is important that n 2 in PTR glass does not vary after UV exposure and thermal development.

Journal of Non-Crystalline Solids, 2001

Second harmonic generation (SHG) in poled glasses opens new opportunities in material research an... more Second harmonic generation (SHG) in poled glasses opens new opportunities in material research and device development for optics. Within this context 1 À xLaMgB 5 O 10 ±xTiO 2 and 1 À xLaMgB 5 O 10 ±xNb 2 O 5 0 6 x 6 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 v 3 have been investigated. A second harmonic signal was observed for each thermally poled composition, except for the LaMgB 5 O 10 matrix glass.

IEEE Journal of Quantum Electronics, 2004

We study the various nonlinear effects produced during the detection of high-intensity signals in... more We study the various nonlinear effects produced during the detection of high-intensity signals in semiconductor photodiodes. Experimental results on few commercial detectors are compared with theoretical analysis. This analysis is based on the tensor coefficients from second-and third-order optical nonlinearities. Both contributions are measured using collinear orthogonally polarized beams in a pump-probe setup. The photoelectric signal is obtained for several orientations of the crystal optic axis.

Http Www Theses Fr, 2000

Mesure de la taille du col du faisceau avec le BeamScan……………….……………… 53 b. Mesure de la taille du... more Mesure de la taille du col du faisceau avec le BeamScan……………….……………… 53 b. Mesure de la taille du col du faisceau avec une simple photodiode…….……………… 55 c. Mesure de la taille du col du faisceau avec une lame et un détecteur…...……………… 55 d. Mesure de la taille du col du faisceau à l'aide du signal non linéaire…...……………… 56 3. MESURE DE LA LONGUEUR D'ONDE. …………………………………………… 57 4. ESTIMATION DE LA LARGEUR TEMPORELLE PAR AUTOCORRELATION (TECHNIQUE CLASSIQUE) …………………………………...………………………………58 a. Autocorrélation utilisant un cristal non linéaire. ………………………..……………… 58 b. Autocorrélation directe dans une photodiode. ………………………….……………… 60 c. Mesure de la largeur temporelle à 400nm. ……………………………... 61 5. PRISE EN COMPTE DE LA FORME TEMPORELLE EXACTE DES IMPULSIONS : « TECHNIQUE CANIONI ». …………………………………...……………………………… 62 C. Conclusion……………………………………………………………………………..…………………64 CHAPITRE III : Mesures d'indices non linéaires en configuration d'absorption transitoire…………… 67 A. Récapitulatif des différentes techniques de mesures de l'indice non linéaire, avantages et inconvénients de chacune.

Journal of the Optical Society of America B, 2004

HAL (Le Centre pour la Communication Scientifique Directe), Nov 2, 2006

Through examining the product of the mathematical variance of intensity with respect to time and ... more Through examining the product of the mathematical variance of intensity with respect to time and frequency, we arrive at a temporal characterization of laser pulses through parameters for pulse duration, group delay dispersion and temporal form. These statistics, which are sufficient to predict subsequent pulse behavior, are recoverable in a simple experiment, measuring the two-photon-induced photocurrents in three nonlinear diodes. With only two photodiodes, we demonstrate that pulse durations as low as several tens of femtoseconds can be easily measured in a single shot if the usual assumptions of pulse form and dispersion are made as in the more difficult autocorrelation setup.

Proceedings of SPIE, Nov 29, 2000

ABSTRACT We present precise and absolute measurements of full complex third order optical suscept... more ABSTRACT We present precise and absolute measurements of full complex third order optical susceptibility on different fused silica and original glasses composed of tellurium, titanium, niobium erbium. These materials are designed to be the key point for applications ranging form high power laser systems to optoelectronics, their nonlinear index of refraction is a major property and thus must be accurately known. Due to the accuracy and sensitivity of our technique, we have been able to find a large dispersion (more than 30%) of the non linear index of fused silica glasses as a function of their processing mode. On the other hand, measurements on tellurium glasses have shown very strong nonlinearities (40 times higher than fused silica), to be linked to the configurations of their cations and anions. Although the titanium and niobium glasses are less nonlinear, they can be promising matrices for addition of luminescent entities like erbium leading to very interesting laser amplification materials. The experimental set-up is a collinear pump-probe (orthogonally polarized) experiment using transient absorption technique. It is built with around a 100 femtosecond laser oscillator. A fast oscillating delay between the pump and the probe allows us to measure the electronic nonlinearity in quasi real-time. This experiment has the following specifications: an absolute measurement accuracy below 10% mainly due to the laser parameters characterization, a relative measurement accuracy of 1% and a resolution less than 5.10-24m2/V2(50 times less than fused silica).

This invention relates to the field of tools determining the chemical composition of a sample.The... more This invention relates to the field of tools determining the chemical composition of a sample.The present invention relates more particularly to an improvement in the detection of chemical elements in a sample by fluorescence emission induced by a laser (LIF: laser Induced fluorescence) .It relates to a system for detecting at least one chemical element in a material comprising at least one laser emitting means to ionize a portion of said material to create a fluorescence, characterized in that it comprises at least one Bragg type of network transmission for filtering the wavelength corresponding to the excitation wavelength of the element and at least one photodiode for detecting the corresponding line said wavelength.

An autocorrelator-like set up is proposed to characterize optical nonlinear effects in a photodio... more An autocorrelator-like set up is proposed to characterize optical nonlinear effects in a photodiode. Experimental results are confronted with theoretical analysis at second and third orders, justifying two photon absorption use in auto-correlators.

Fourier Transform Spectroscopy/ Hyperspectral Imaging and Sounding of the Environment, 2007

ABSTRACT In the framework of spatial aperture synthesis, we developed a temporal aperture synthes... more ABSTRACT In the framework of spatial aperture synthesis, we developed a temporal aperture synthesis allowing the concatenation of several interferograms. We succeed to enhance the resolving power of static Fourier-transform spectrometers by a factor of 40.

2006 Northern Optics, 2006

By examining the first- and second-order moments of intensity with respect to time and frequency,... more By examining the first- and second-order moments of intensity with respect to time and frequency, we arrive at a temporal characterization of laser pulses through parameters for pulse duration, group delay dispersion and temporal form. These parameters, which are sufficient to predict subsequent pulse behavior, are recoverable in a simple experiment, measuring the two-photon-induced photocurrents in three nonlinear diodes. With only two photodiodes, we demonstrate that pulse durations as low as several tens of femtoseconds can be easily measured in a single shot, if the usual assumptions of pulse form and dispersion are made as in the more difficult autocorrelation setup.

Optical Materials, 2006

Nonlinear properties of a photo-thermo-refractive (PTR) glass are studied and compared with those... more Nonlinear properties of a photo-thermo-refractive (PTR) glass are studied and compared with those in fused silica and a conventional optical glass. PTR glass is a new photosensitive medium for high-efficiency phase volume hologram recording which manifests a linear refractive index modulation after exposure to UV radiation followed by thermal treatment. Nonlinear optical properties of PTR glass exposed to femtosecond laser pulses are studied. Diffraction patterns in a propagated laser beam focused in the sample were detected by a CCD, while a nonlinear refractive index was measured by a collinear-orthogonal-polarizationpump-probe (COP3) method. It was found that nonlinear refractive index of PTRG is n 2 = 3.3 • 10 À20 m 2 /W (0.33 ppm cm 2 / GW) which is about the same as for the fused silica. It is important that n 2 in PTR glass does not vary after UV exposure and thermal development.

Journal of Non-Crystalline Solids, 2001

Second harmonic generation (SHG) in poled glasses opens new opportunities in material research an... more Second harmonic generation (SHG) in poled glasses opens new opportunities in material research and device development for optics. Within this context 1 À xLaMgB 5 O 10 ±xTiO 2 and 1 À xLaMgB 5 O 10 ±xNb 2 O 5 0 6 x 6 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 v 3 have been investigated. A second harmonic signal was observed for each thermally poled composition, except for the LaMgB 5 O 10 matrix glass.

IEEE Journal of Quantum Electronics, 2004

We study the various nonlinear effects produced during the detection of high-intensity signals in... more We study the various nonlinear effects produced during the detection of high-intensity signals in semiconductor photodiodes. Experimental results on few commercial detectors are compared with theoretical analysis. This analysis is based on the tensor coefficients from second-and third-order optical nonlinearities. Both contributions are measured using collinear orthogonally polarized beams in a pump-probe setup. The photoelectric signal is obtained for several orientations of the crystal optic axis.

Http Www Theses Fr, 2000

Mesure de la taille du col du faisceau avec le BeamScan……………….……………… 53 b. Mesure de la taille du... more Mesure de la taille du col du faisceau avec le BeamScan……………….……………… 53 b. Mesure de la taille du col du faisceau avec une simple photodiode…….……………… 55 c. Mesure de la taille du col du faisceau avec une lame et un détecteur…...……………… 55 d. Mesure de la taille du col du faisceau à l'aide du signal non linéaire…...……………… 56 3. MESURE DE LA LONGUEUR D'ONDE. …………………………………………… 57 4. ESTIMATION DE LA LARGEUR TEMPORELLE PAR AUTOCORRELATION (TECHNIQUE CLASSIQUE) …………………………………...………………………………58 a. Autocorrélation utilisant un cristal non linéaire. ………………………..……………… 58 b. Autocorrélation directe dans une photodiode. ………………………….……………… 60 c. Mesure de la largeur temporelle à 400nm. ……………………………... 61 5. PRISE EN COMPTE DE LA FORME TEMPORELLE EXACTE DES IMPULSIONS : « TECHNIQUE CANIONI ». …………………………………...……………………………… 62 C. Conclusion……………………………………………………………………………..…………………64 CHAPITRE III : Mesures d'indices non linéaires en configuration d'absorption transitoire…………… 67 A. Récapitulatif des différentes techniques de mesures de l'indice non linéaire, avantages et inconvénients de chacune.

Journal of the Optical Society of America B, 2004