Damien Jamon

Magneto-optical waveguides made of cobalt ferrite nanoparticles embedded in silica/zirconia organic-inorganic matrix

This paper describes a way to develop magneto-optical waveguides via sol-gel process. They are made of cobalt ferrite nanoparticles embedded in a silica/zirconia matrix. Thin films are coated on glass substrate using the dip-coating technique. Annealing and UV treatment are applied to finalize sample preparation. Therefore, planar waveguides combining magneto-optical properties with a low refractive index (≈1,5) are obtained. M-lines and free space ellipsometry measurements show a specific Faraday rotation of 250°/cm and a modal birefringence of 1×10−4 at 820 nm. Thus, the mode conversion efficiency can reach a maximum value around 56%.

Optical properties of silver nanoparticles thermally grown in a mesostructured hybrid silica film

The composition, the structure and the optical properties of mesostructured hybrid silica films elaborated by sol-gel routine are studied versus the temperature of the post treatment by comparing ellipsometric measurements, atomic force microscopy and electronic microscopy characterizations, X-ray diffraction and thermal analysis. This paper shows that the refractive index variation is a combination between the structure contraction, the solvent evaporation, the silica wall condensation and the pyrolysis of the copolymer. We also investigate the optical properties of thermally grown silver nanoparticles in the mesotructured films and we demonstrate that these properties depend on the optical properties of the host matrix and on the silver concentration profile in the film.

Magneto-optical nanoparticle-doped silica-titania planar waveguides

This letter describes how composite material, made of maghemite (γ‐Fe2O3) nanoparticles embedded in a silica∕titania matrix, can be used to develop new magneto-optical planar waveguides. Thin film samples are coated on Pyrex™ substrates from a magnetic particles doped sol-gel preparation. M-lines spectroscopy measurements performed on these samples show that an out of plane magnetic field applied during the gelation induces a decrease of the planar waveguide phase mismatch. Free space measurements evidence the Faraday rotation of the films up to 25°∕cm at 633 nm. Improvements and leads of further works are proposed in term of magneto-optical waveguide applications.

Experimental investigation of longitudinal magneto-optic effects in four ferrite ferrofluids in visible-near infrared spectrum

We present an extensive experimental work concerning measurement of longitudinal magneto-optic effects (Faraday rotation and circular dichroism) induced in magnetic liquids. Seven ferrofluid samples allow the study of the influence of numerous parameters: magnetic suspension and carrier liquid characteristics, magnetic field strength (up to 10 kOe) and frequency (dc to 50 kHz), light wavelength (400 to 2000 nm) and, temperature (253 to 373 K). These topics, especially the spectral area, have rarely been studied before. Most of the studies show interesting behaviors and aid in the understanding of magneto-induced phenomena. They also contribute to the conception of new optical applications of ferrofluids: 1) a pure Faraday rotator (free of circular dichroism) obtained by a ferrofluid mixing method and 2) a Faraday light modulator working up to 50 kHz.

Hybrid magneto-optical mode converter made with a magnetic nanoparticles-doped SiO2/ZrO2 layer coated on an ion-exchanged glass waveguide

This paper describes the possibility to achieve a TE-TM mode conversion in a magneto-optical hybrid waveguide operating at λ = 1550 nm. This hybrid device is made by coating a SiO2/ZrO2 layer doped with magnetic nanoparticles on an ion-exchanged glass waveguide. Soft annealing (90 °C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of lateral confinement and mode conversion. Indeed, TE to TM mode conversion has been observed when a longitudinal magnetic field is applied to the device. The amount of this conversion is discussed taking into account the distribution of light between the layer and the guide, and the modal birefringence of the structure.

Optical investigation of /spl gamma/-Fe/sub 2/O/sub 3/ nanoparticle-doped silica gel matrix for birefringent components

We present an optical study of silica gel matrix doped with maghemite /spl gamma/-Fe/sub 2/O/sub 3/ nanoparticles originating from a ferrofluid. This work is a preliminary study for building adjusted birefringent components suitable for ellipsometry. Silica gel matrix is obtained as sol-gel synthesis. Results show that pure and doped samples solidified out of a magnetic field are quasi-isotropic, whereas samples solidified in the presence of a magnetic field exhibit a very large permanent linear birefringence comparable to that produced by the ferrofluid under the same magnetic field.

Magnetic nanoparticles-doped silica layer reported on ion-exchanged glass waveguide: towards integrated magneto-optical devices

In the framework of optical telecommunication systems, many functions are integrated on the same substrate. Nevertheless, one of the most important, such as isolation, is achieved using discrete components. It is based on magnetic materials which are always difficult to integrate with classical technologies. This is due to the annealing temperature of magnetic materials. In this paper we present another way for the realisation of such components. We use a dip coating process to report a magnetic nanoparticles doped silica layer on ion-exchanged glass waveguide. The advantages of this method is discussed and we demonstrate its compatibility with ion-exchanged technology. By varying the refractive index of the layer, we can adjust the interaction between the waveguide and the magneto-optical layer.

Chirality distribution in single walled carbon nanotube films by spectroscopic ellipsometry

We report an experimental technique that determines the chirality distribution in single wall carbon nanotube (SWCNT) films. Films of CoMoCat SWCNTs and SWCNTs enriched in (6,5) chirality are considered. Classical methods like photoluminescence spectroscopy frequently give incomplete distribution. In this way, spectroscopic ellipsometry is used to determine the dielectric function of SWCNT film. The chirality abundance obtained by analysing the ellipsometric data with a tight binding model is compared with that deduced from photoluminescence excitation spectroscopy. We demonstrate that ellipsometry is an efficient tool for a complete and quantitative determination of the chirality distribution and the metallic/semiconducting ratio.

Integrated Broadband Polarization Splitters Made by Ion-Exchange on Glass

In this letter, we present the design, fabrication, and characterization of a broadband polarization splitter working in the 1550-nm transmission window. The device is an asymmetric Y-junction realized by Ag+/Na+ ion exchange on glass. The transverse electric (TE) output branch of the device filters out the residual transverse magnetic (TM) mode by radiation. Measurements show cross-talks better than (31.1±0.4) dB in TE and better than (32.7±0.4) dB in TM mode over a 70-nm bandwidth limited by the characterization source. Optimal values of, respectively, (33.6±0.4) dB and (37.2±0.4) dB were measured at 1540 nm. At this wavelength, the insertion losses are, respectively, (6.0±0.4) dB and (5.5±0.4) dB in TE and TM modes while the function losses are (0.65±0.12) dB and (0.35±0.12) dB, respectively.

Accurate and rapid optical characterization of an anisotropic guided structure based on a neural method.

Optimal performances of integrated optical devices are obtained by the use of an accurate and reliable characterization method. The parameters of interest, i.e., optical indices and thickness of the waveguide structure, are calculated from effective indices by means of an inversion procedure. We demonstrate how an artificial neural network can achieve such a process. The artificial neural network used is a multilayer perceptron. The first result concerns a simulated anisotropic waveguide. The accuracy in the determination of optical indices and waveguide thickness is 5 x 10(-5) and 4 nm, respectively. Then an experimental application on a silica-titania thin film is performed. In addition, effective indices are measured by m-lines spectroscopy. Finally, a comparison with a classical optimization algorithm demonstrates the robustness of the neural method.