References of "Blanche, Pierre-Alexandre"
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See detailVolume phase holographic gratings: large size and high diffraction efficiency
Blanche, Pierre-Alexandre ULg; Gailly, Patrick ULg; Habraken, Serge ULg et al

in Optical Engineering (2004), 43(11), 2603-2612

Volume phase holographic gratings (VPHGs) possess unique properties that make them attractive for numerous applications. After reviewing major VPHG characteristics through theory, we discuss some aspects ... [more ▼]

Volume phase holographic gratings (VPHGs) possess unique properties that make them attractive for numerous applications. After reviewing major VPHG characteristics through theory, we discuss some aspects of the dichromated gelatin recording material and the holographic recording process. The large-scale VPHG research facility set up at the Center Spatial de Liege enables production of VPHGs up to 380 mm in diameter, with fringe frequencies from 315 to 3300 Ip/mm. We describe the work that has been undertaken in our laboratory to remove the last limitations inherent in VPHGs. (C) 2004 Society of Photo-Optical Instrumentation Engineers. [less ▲]

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See detailPolarization holography reveals the nature of the grating in polymers containing azo-dye
Blanche, Pierre-Alexandre ULg; Lemaire, P. C.; Maertens, Christophe et al

in Optics Communications (2000), 185(1-3), 1-12

To study the origin of reversible holographic recording in three polymers containing the same azo-dye, we have measured the diffraction efficiency and analyzed the gratings characteristics for various ... [more ▼]

To study the origin of reversible holographic recording in three polymers containing the same azo-dye, we have measured the diffraction efficiency and analyzed the gratings characteristics for various writing beams polarizations. The amplitude of the holographic grating, as well as the ratio between index and absorption modulations, have been investigated by gratings shifting. The total amount of diffracted power and the diffraction efficiency versus the reading beam polarization has been measured by non-degenerated four waves mixing. These experiments have revealed that the molecular mechanisms of holographic recording in the studied compounds are different. The photoinduced orientation of the chromophores is predominant for C6-C11-DMNPAA; so, in C11-C6-DMNPAA (DMNPAA: 2,5-dimethyl-4-(p-nitrophenylazo)anisole), the refractive index variation comes from the presence of both trans and cis populations generated by photoisomerization. The behavior of the PVK:DMNPAA is included between these extreme cases since both phenomena act. [less ▲]

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See detailPhotoinduced birefringence and diffraction efficiency in azo dye doped or grafted polymers: theory versus experiment of the temperature influence
Blanche, Pierre-Alexandre ULg; Lemaire, P. C.; Maertens, Christophe et al

in Journal of the Optical Society of America. B, Optical Physics (2000), 17(5), 729-740

We have investigated the influence of the temperature on the photoinduced birefringence as well as on the diffraction efficiency of azo dye doped or grafted polymers. The samples are composed of three ... [more ▼]

We have investigated the influence of the temperature on the photoinduced birefringence as well as on the diffraction efficiency of azo dye doped or grafted polymers. The samples are composed of three polymer matrices containing 2, 5-dimethyl-4-(p-nitrophenylazo anisole). We propose two theoretical models to explain the experimental increase of both phenomena when the temperature is decreased. Models are based on the statistical angular distribution of the chromophores that depends on the intensity of the polarized laser beam in the media, counteracted by the thermal agitation. Parameters introduced in both models can be used to characterize the polymeric system properties. [less ▲]

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See detailSynthesis and polarized light-induced birefringence of new polymethacrylates containing carbazolyl and azobenzene pendant groups
Maertens, Christophe; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part B, Polymer Physics (2000), 38(1), 205-213

Low Tg copolymers of [11(N-carbazolyl)undecylmethacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]-phenoxyalkylmethacrylate] have been synthesized and the polarized light-induced birefringence of ... [more ▼]

Low Tg copolymers of [11(N-carbazolyl)undecylmethacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]-phenoxyalkylmethacrylate] have been synthesized and the polarized light-induced birefringence of thick films (70 m) has been investigated at a constant deducted temperature relative to Tg (T - Tg = 10 °C). The optical properties of these copolymers have been studied in relation to the azo-dye content and the length of the alkyl spacer between the azo-dye and the methacrylic backbone. They have been compared with the dispersion of (4-methoxy-2,5-dimethylphenyl)-(4-nitrophenyl)diazene (DMNPAA) within a poly[11(N-carbazolyl)undecyl-methacrylate] and a poly[N-vinylcarbazole] (PVK) matrix. The experimental curves have been fitted by biexponentials, so emphasizing the effects of the copolymer structure on the kinetics of the writing process. The photoinduced orientation is more than three orders of magnitude higher in a grafted material compared to the dispersion version. The azo-dye concentration also has an important role in both the amplitude and the dynamics of the photo-orientation. [less ▲]

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See detailTemperature variation of the photoinduced birefringence of an azo dye doped polymer
Blanche, Pierre-Alexandre ULg; Lemaire, Philippe ULg; Maertens, Christophe et al

in Polymer Engineering & Science (1999), 39(3), 406-412

The influence of the temperature on the photoinduced birefringence on an azo dye doped polymer film has been studied. Sample is composed of a polymer matrix PVK (Poly(N-vinylcarbazole)), doped with 10 ... [more ▼]

The influence of the temperature on the photoinduced birefringence on an azo dye doped polymer film has been studied. Sample is composed of a polymer matrix PVK (Poly(N-vinylcarbazole)), doped with 10 weight percent (wt%) of the birefringent molecule DMNPAA (2,5-dimethyl-4-(p-nitrophenylazo)anisole) and 30 wt% of ECZ (N-ethylcarbazole) which acts as a plasticizer. Theoretical results can explain the behavior of the amplitude of the photoinduced birefringence versus temperature. Experimental and theoretical results are compared. Holographic recording experiments based on photoinduced birefringence have been carried out. Based on the effect of temperature, we have been able to significantly increase the diffraction efficiency of our sample. [less ▲]

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See detailDynamics of the photo-induced orientation and relaxation of new polymethacrylates containing carbazolyl and azobenzene pendant groups
Maertens, Christophe; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Polymer International (1999), 48(3), 205-211

Polarized-light-induced birefringence has been investigated in copolymers of [-(N-carbazolyl)alkyl methacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]phenoxyalkyl methacrylate]. Optical properties ... [more ▼]

Polarized-light-induced birefringence has been investigated in copolymers of [-(N-carbazolyl)alkyl methacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]phenoxyalkyl methacrylate]. Optical properties of the side-chain copolymers have been compared with materials in which the azo-dye was merely dispersed in a poly[-(N-carbazolyl)alkyl methacrylate] matrix. Increasing the temperature of the film has a dramatic depressive effect on the maximum of photo-induced orientation near and above the glass transition temperature (Tg) region, while its effect was restricted under this temperature. Kinetics of the photo-orientation and the thermal relaxation as a function of temperature have been analysed by a biexponential model based on two rate constants. The universal Williams-Landel-Ferry (WLF) theory has been used to correlate the writing process and relaxation relative time constants with the relative temperature, i.e. T-Tg . The validity of this model for the studied materials leads to the assumption that photo-orientation and relaxation processes are mainly dependent on the free volume in the polymer matrix. This hypothesis has been assessed in the case of [11-(N-carbazolyl)undecyl methacrylate]-based materials. [less ▲]

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See detailPolarised light induced birefringence in azo dye doped polymer: a new model and polarised holographic experiments
Blanche, Pierre-Alexandre ULg; Lemaire, P. C.; Maertens, Christophe et al

in Optics Communications (1997), 139(1-3), 92-98

The photoinduced birefringence of azo dye DMNPAA (2,5-dimelthyl-4-(p-nitrophenylazo)anisole) in PVK (Poly(N-vinylcarbazole)) thin film is reported. A two-layer model of the film is proposed to take into ... [more ▼]

The photoinduced birefringence of azo dye DMNPAA (2,5-dimelthyl-4-(p-nitrophenylazo)anisole) in PVK (Poly(N-vinylcarbazole)) thin film is reported. A two-layer model of the film is proposed to take into account the different results obtained in photoinduced birefringence experiments. According to this model, the sample exhibits intrinsic birefringence but the absorbed light can induce orientation of the optically active molecules contained in the first layer of the film, lending to photoinduced birefringence. Holographic experiments have been carried out in this media with recording at 514 nm and readout at 633 nm. Diffraction efficiency versus polarisation shows that these polymers can record polarisation states as well as intensity patterns. [less ▲]

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See detailBeam-foil spectroscopy of Ne IV
Bastin, Thierry ULg; Blanche, Pierre-Alexandre ULg; Garnir, Henri-Pierre ULg et al

Poster (1994)

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