Photosensitive Materials: Optical properties and applications

Les matériaux photosensibles sont des matériaux (organique ou inorganique) dont l’indice de réfraction peut être localement modifié lorsqu’ils sont soumis à une excitation lumineuse dont une partie de l’énergie est absorbée par ce matériau. La majorité des travaux réalisés dans ce domaine a longtemps concerné des applications d’optique guidée (fibre ou guides planaires). L’apparition récente de nouveaux matériaux a rendu possible l’utilisation de ce phénomène de photosensibilité dans des composants optiques massifs en permettant notamment la réalisation d'hologrammes de volume à hautes performances. Dans le cadre de ces travaux, un verre inorganique a fait l’objet d’études approfondies : il s’agit d’un verre photo-thermo-réfractif (PTR), pour lequel la variation d’indice est obtenue par exposition à un rayonnement ionisant suivie d’un traitement thermique. La nature même du matériau lui procure des propriétés compatibles avec les contraintes des applications lasers à haute énergie.La première partie de ce manuscrit présente donc l’ensemble des travaux qui ont été réalisés sous ma responsabilité dans le but de mettre en évidence l’inter-relation qui existe entre les propriétés optiques (photosensibilité, absorption, diffusion, interaction laser-matière, propriétés spectrales) et les propriétés structurales de ces verres. La deuxième partie de ce manuscrit présente différentes applications de ces verres d’un point de vue composants, que ce soit pour du filtrage à bande très étroite, la fabrication de masques de phase volumiques, l’étirement ou la compression d’impulsions ultra-courtes ou le développement de nouveaux designs de sources lasers. Enfin, la troisième partie de ce manuscrit présente l’ensemble des réalisations dans lesquelles j’ai été impliqué durant ces 10 dernières années, que ce soit en termes de production scientifique, de management de projets ou d’encadrement de recherches

Broadband antireflection coatings for visible and infrared ranges

International audienceAntireflection coatings are critical elements for space applications as they will influence the overall performances of optical systems. They are among the most classical elements that are produced with optical coatings but remain a challenge when high performances are required. In this paper, we present some recent results based on thin film technology for the production of antireflection coatings dedicated to visible, near-IR and mid-IR spectral ranges. We first present a theoretical and experimental study of broadband antireflection coatings for [400-1100] nm spectral range. We then show antireflection coatings covering the [1.5-15] µm range. Experimental demonstrations and limitations are presented

High performance thin-film optical filters with stress compensation

International audienceWe present a thorough description of high performance thin-film optical filters with high flatness. These components can combine several tens or hundreds of layers and are manufactured using plasma-assisted reactive magnetron sputtering. Stress compensation is achieved using dual side coatings with appropriate spectral function. Examples of highly reflecting mirrors at 515 nm with 15 nm flatness peak-to-valley over up to 75 mm diameter aperture, narrow bandpass filters and filters with broadband controlled transmission are described

Process of production of high efficiency diffractive and refractive optical elements in multicomponent silicate glass by nonlinear photo ionization followed by thermal development.

Apparatus, methods and systems for production of high efficiency refractive and diffractive elements by providing a photo-sensitizer fi-ee multicomponent glass, exposing the multi component glass to pulsed laser radiation to produce refractive indexed modulation, and heating the exposed multicomponent silicate glass to produce the high efficiency refractive and diffractive elements. The pulsed laser radiation is infrared femtosecond pulses to ultraviolet nanosecond pulses which provide ionization of glass matrix. The multicomponent glass is a photosensitive glass with high transparency in ultraviolet spectral region, e.g. silicate glass which includes silver, fluorine and bromine and does not contain photosensitizers such as cerium and antimony, PTR glass, cerium free PTR glass and cerium + antimony free PTR glass

Fast interrogation wavelength tuning for all-optical photoacoustic imaging

Optical detection of ultrasound for photoacoustic imaging provides large bandwidth and high sensitivity at high acoustic frequencies. Higher spatial resolutions can therefore be achieved using Fabry-P\'erot cavity sensors, as compared to conventional piezoelectric detection. However, fabrication constraints during deposition of the sensing polymer layer require a precise control of the interrogation beam wavelength to provide optimal sensitivity. This is commonly achieved by employing slowly tunable narrowband lasers as interrogation sources, hence limiting the acquisition speed. We propose instead to use a broadband source and a fast tunable acousto-optic filter to adjust the interrogation wavelength at each pixel within a few microseconds. We demonstrate the validity of this approach by performing photoacoustic imaging with a highly inhomogeneous Fabry-P\'erot sensor.Comment: 9 pages, 4 figure

Switching waves-induced broadband Kerr frequency comb in fiber Fabry-Perot resonators

We report the generation of broadband frequency combs in fiber Fabry-Perot resonators in the normal dispersion regime enabled by the excitation of switching waves. We theoretically characterise the process by means of a transverse linear stability analysis of the Lugiato-Lefever equation, enabling precise prediction of the switching waves' frequencies. Experimentally, we employed a pulsed-pump fiber Fabry-Perot resonator operating in the normal dispersion regime, integrated into an all-fiber experimental setup. The synchronisation mismatch and the influence of dispersion is thoroughly discussed, unveiling the potential to generate a frequency comb spanning over 15 THz bandwidth, specifically leveraging a flattened low dispersion cavity

Laser Pulse Temporal, Spectral And Spatial Shaping Devices Based On Volume Diffractive Gratings With Variable Parameters

Recent invention of longitudinally chirped volume Bragg gratings has dramatically changed a design of high power femtosecond lasers. Replacing of bulky pairs of conventional surface gratings with compact and robust chirped volume Bragg gratings for stretching and compression of laser pulses in chirped-pulse-amplification systems enabled decrease of size and weight of those systems by several times. This patent application enables substantial increase of stretching time and compression to shorter pulses along with more complex shaping of laser pulses in both temporal and spectral domains

28 THz soliton frequency comb in a continuous-wave pumped fiber Fabry-Perot resonator

We report the generation of an optical frequency comb featuring 28 THz bandwidth, sustained by a single 80 fs cavity soliton recirculating in a fiber Fabry-Perot resonator. This large spectrum is comparable to frequency combs obtained with microresonators operating in the anomalous dispersion regime. Thanks to the compact design and the easy coupling of the resonator, cavity solitons can be generated in an all-fiber experimental setup with a continuous wave pumping scheme. We also observe the generation of a dispersive wave at higher frequencies which is supported by higher-order dispersion. These observations align remarkably well with both numerical simulations and the established theory of cavity solitons.Comment: 6 pages, 6 figure

Photosensitive chalcogenide metasurfaces supporting bound states in the continuum

International audienceWe study, both theoretically and experimentally, tunable metasurfaces supporting sharp Fano-resonances inspired by optical bound states in the continuum. We explore the use of arsenic trisulfide (a photosensitive chalcogenide glass) having optical properties which can be finely tuned by light absorption at the post-fabrication stage. We select the resonant wavelength of the metasurface corresponding to the energy below the arsenic trisulfide bandgap, and experimentally control the resonance spectral position via exposure to the light of energies above the bandgap