Laurent Dupont - Academia.edu (original) (raw)

Papers by Laurent Dupont

Research paper thumbnail of Isotropic Elastic Stress Induced Large Temperature Range Liquid Crystal Blue Phase at Room Temperature

Journal of physical chemistry & biophysics, Jan 11, 2016

A thermodynamically stable blue phase (BP) based on the conventional rod like nematogen is demons... more A thermodynamically stable blue phase (BP) based on the conventional rod like nematogen is demonstrated for the first time at room temperature by only diluting a chiral-nematic mixture with the help of some nonmesogenic isotropic liquid. It is observed that addition of this isotropic liquid does not only stabilize the BPs at room temperature, but also significantly improves the temperature range (reversible during heating and cooling) of the BPs to the level of more than 28 °C. Apart from that, we have observed its microsecond electro-optic response time and, external electric field induced wavelength tuning, which are the two indispensable requirements for next generation optical devices, photonic displays, lasers, and many more. Here we propose that the isotropic liquid plays two crucial roles simultaneously. On one hand, it reduces the effective elastic moduli (EEM) of the BP mixtures and stabilizes the BPs at room temperature, and on the other hand, it increases the symmetry of ...

Research paper thumbnail of Dispersions of Goethite Nanorods in Aprotic Polar Solvents

Materials (Basel, Switzerland), Jan 17, 2017

Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crys... more Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crystalline phases beyond some concentration threshold. These phases often respond to electric and magnetic fields. At lower concentrations, usual isotropic liquids are observed but they can display very strong Kerr and Cotton-Mouton effects (i.e., field-induced particle orientation). For many examples of these colloidal suspensions, the solvent is water, which hinders most electro-optic applications. Here, for goethite (α-FeOOH) nanorod dispersions, we show that water can be replaced by polar aprotic solvents, such as-methyl-2-pyrrolidone (NMP) and dimethylsulfoxide (DMSO), without loss of colloidal stability. By polarized-light microscopy, small-angle X-ray scattering and electro-optic measurements, we found that the nematic phase, with its field-response properties, is retained. Moreover, a strong Kerr effect was also observed with isotropic goethite suspensions in these polar aprotic sol...

Research paper thumbnail of A comparison of possible disclination mechanisms of switching in thin ferroelectric liquid crystal samples

Research paper thumbnail of Planar-Homeotropic Transition in PS-FLC Induced by an Electric Field During Photopolymerization in the Nematic Phase

Molecular Crystals and Liquid Crystals

We studied a polymer-stabilized ferroelectric liquid crystal presenting a high polymer concentrat... more We studied a polymer-stabilized ferroelectric liquid crystal presenting a high polymer concentration. These structures exhibit strong interaction between both components of the mixture. This can be demonstrated by applying an electric field during polymerization: it is thus possible to fix both the tilt angle of the director in all mesogenic phases and the layer tilt in the smectic phase.

Research paper thumbnail of Device for spatially modulating a light beam and corresponding uses

Research paper thumbnail of Mach-Zehner interferometric coupler with single-mode optical fibre

Research paper thumbnail of Electric birefringence and electric dichroism of goethite colloidal suspensions

Research paper thumbnail of Device for controlling the polarization of a signal carried in the form of a light beam, and corresponding application

Research paper thumbnail of Device for Controlling Polarization of a Signal Carried in the Form of a Light Beam, and Corresponding Application

Research paper thumbnail of Manufacturing method of a device for attenuating a signal carried by an optical fiber, attenuation device, attenuation system and corresponding applications

Research paper thumbnail of Liquid crystal ferroelectric electro-optical phase modulators which are insensitive to polarization

Research paper thumbnail of Dynamic spatial equalizer based an a spatial light modulator

Research paper thumbnail of Dynamic spatial equalizer based on a spatial light modulator

Research paper thumbnail of Manufacturing method of a device attenuating a signal transported by an optical fibre, attenuating device, attenuating systems and corresponding applications

Research paper thumbnail of Atténuateur variable fibré à base de cristal liquide

Research paper thumbnail of Design and Fabrication of a Tunable InP-based VCSEL using a Electro-Optic Index Modulator

2006 International Conference on Indium Phosphide and Related Materials Conference Proceedings, 2006

We present the first vertical surface emitting laser (VCSEL) operating at 1.55-µm comprising a el... more We present the first vertical surface emitting laser (VCSEL) operating at 1.55-µm comprising a electro-optic modulator inside its cavity. This material consists of nematic liquid crystal dispersed in a polymer material (nano-PDLC). This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The nano-PDLC layer length, close to 6 µm, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 µs to scan the full spectral range, making this device appropriate for some access network functions. This first version is optically pumped and requires 170 volts to obtain a 10 nm tunability.

Research paper thumbnail of Contrôleur de polarisation rapide à cristaux liquides pour la compensation de PMD du premier ordre

Research paper thumbnail of Extension de budget optique de systèmes d'accès FTTH à l'aide de SOA

Research paper thumbnail of Réalisation de micro résonateurs intégrés en polymère et de fonctions associées

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of <title>1.55-μm optically pumped tunable VCSEL based on a nano-polymer dispersive liquid crystal phase modulator</title>

Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 2006

We present a new approach to achieve tunability on a 1.55 µm vertical cavity surface emitting las... more We present a new approach to achieve tunability on a 1.55 µm vertical cavity surface emitting laser (VCSEL). Tunability is achieved thanks to an electro-optic index modulator. This electro-optic material consists in a n-PDLC phase layer introduced inside the VCSEL cavity. N-PDLC comprises nematic liquid crystal dispersed in a polymer material. This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The n-PDLC layer length, close to 6 µm, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 µs to scan the full spectral range, making this device appropriate for some access network functions. Voltage values are the main limiting factor, 170 Volts have been required to obtain 10 nm tunability, but material engineering is in progress to improve this point. We presented a first version of the device optically pumped, the next version will be electrically pumped as required for access network applications targeted here.

Research paper thumbnail of Isotropic Elastic Stress Induced Large Temperature Range Liquid Crystal Blue Phase at Room Temperature

Journal of physical chemistry & biophysics, Jan 11, 2016

A thermodynamically stable blue phase (BP) based on the conventional rod like nematogen is demons... more A thermodynamically stable blue phase (BP) based on the conventional rod like nematogen is demonstrated for the first time at room temperature by only diluting a chiral-nematic mixture with the help of some nonmesogenic isotropic liquid. It is observed that addition of this isotropic liquid does not only stabilize the BPs at room temperature, but also significantly improves the temperature range (reversible during heating and cooling) of the BPs to the level of more than 28 °C. Apart from that, we have observed its microsecond electro-optic response time and, external electric field induced wavelength tuning, which are the two indispensable requirements for next generation optical devices, photonic displays, lasers, and many more. Here we propose that the isotropic liquid plays two crucial roles simultaneously. On one hand, it reduces the effective elastic moduli (EEM) of the BP mixtures and stabilizes the BPs at room temperature, and on the other hand, it increases the symmetry of ...

Research paper thumbnail of Dispersions of Goethite Nanorods in Aprotic Polar Solvents

Materials (Basel, Switzerland), Jan 17, 2017

Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crys... more Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crystalline phases beyond some concentration threshold. These phases often respond to electric and magnetic fields. At lower concentrations, usual isotropic liquids are observed but they can display very strong Kerr and Cotton-Mouton effects (i.e., field-induced particle orientation). For many examples of these colloidal suspensions, the solvent is water, which hinders most electro-optic applications. Here, for goethite (α-FeOOH) nanorod dispersions, we show that water can be replaced by polar aprotic solvents, such as-methyl-2-pyrrolidone (NMP) and dimethylsulfoxide (DMSO), without loss of colloidal stability. By polarized-light microscopy, small-angle X-ray scattering and electro-optic measurements, we found that the nematic phase, with its field-response properties, is retained. Moreover, a strong Kerr effect was also observed with isotropic goethite suspensions in these polar aprotic sol...

Research paper thumbnail of A comparison of possible disclination mechanisms of switching in thin ferroelectric liquid crystal samples

Research paper thumbnail of Planar-Homeotropic Transition in PS-FLC Induced by an Electric Field During Photopolymerization in the Nematic Phase

Molecular Crystals and Liquid Crystals

We studied a polymer-stabilized ferroelectric liquid crystal presenting a high polymer concentrat... more We studied a polymer-stabilized ferroelectric liquid crystal presenting a high polymer concentration. These structures exhibit strong interaction between both components of the mixture. This can be demonstrated by applying an electric field during polymerization: it is thus possible to fix both the tilt angle of the director in all mesogenic phases and the layer tilt in the smectic phase.

Research paper thumbnail of Device for spatially modulating a light beam and corresponding uses

Research paper thumbnail of Mach-Zehner interferometric coupler with single-mode optical fibre

Research paper thumbnail of Electric birefringence and electric dichroism of goethite colloidal suspensions

Research paper thumbnail of Device for controlling the polarization of a signal carried in the form of a light beam, and corresponding application

Research paper thumbnail of Device for Controlling Polarization of a Signal Carried in the Form of a Light Beam, and Corresponding Application

Research paper thumbnail of Manufacturing method of a device for attenuating a signal carried by an optical fiber, attenuation device, attenuation system and corresponding applications

Research paper thumbnail of Liquid crystal ferroelectric electro-optical phase modulators which are insensitive to polarization

Research paper thumbnail of Dynamic spatial equalizer based an a spatial light modulator

Research paper thumbnail of Dynamic spatial equalizer based on a spatial light modulator

Research paper thumbnail of Manufacturing method of a device attenuating a signal transported by an optical fibre, attenuating device, attenuating systems and corresponding applications

Research paper thumbnail of Atténuateur variable fibré à base de cristal liquide

Research paper thumbnail of Design and Fabrication of a Tunable InP-based VCSEL using a Electro-Optic Index Modulator

2006 International Conference on Indium Phosphide and Related Materials Conference Proceedings, 2006

We present the first vertical surface emitting laser (VCSEL) operating at 1.55-µm comprising a el... more We present the first vertical surface emitting laser (VCSEL) operating at 1.55-µm comprising a electro-optic modulator inside its cavity. This material consists of nematic liquid crystal dispersed in a polymer material (nano-PDLC). This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The nano-PDLC layer length, close to 6 µm, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 µs to scan the full spectral range, making this device appropriate for some access network functions. This first version is optically pumped and requires 170 volts to obtain a 10 nm tunability.

Research paper thumbnail of Contrôleur de polarisation rapide à cristaux liquides pour la compensation de PMD du premier ordre

Research paper thumbnail of Extension de budget optique de systèmes d'accès FTTH à l'aide de SOA

Research paper thumbnail of Réalisation de micro résonateurs intégrés en polymère et de fonctions associées

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of <title>1.55-μm optically pumped tunable VCSEL based on a nano-polymer dispersive liquid crystal phase modulator</title>

Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 2006

We present a new approach to achieve tunability on a 1.55 µm vertical cavity surface emitting las... more We present a new approach to achieve tunability on a 1.55 µm vertical cavity surface emitting laser (VCSEL). Tunability is achieved thanks to an electro-optic index modulator. This electro-optic material consists in a n-PDLC phase layer introduced inside the VCSEL cavity. N-PDLC comprises nematic liquid crystal dispersed in a polymer material. This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The n-PDLC layer length, close to 6 µm, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 µs to scan the full spectral range, making this device appropriate for some access network functions. Voltage values are the main limiting factor, 170 Volts have been required to obtain 10 nm tunability, but material engineering is in progress to improve this point. We presented a first version of the device optically pumped, the next version will be electrically pumped as required for access network applications targeted here.