G. Vitrant

Control of Semiconductor Particle Size in Sol-Gel Thin Films

Thin silica and silica-titania films containing CdS and PbS quantum size particles were obtained by separate preparation of the matrix and the colloidal sols and successive mixing. Sulfide particles were obtained by reaction of metal acetates with thioacetamide and control of particle size was achieved by surface capping agents. Powders and thin films deposited on soda-lime slides were prepared and characterized by XRD. Absorption spectra were recorded on films. The nonlinear refractive index was measured by anm-line technique on a CdS-doped sample. The nonlinear effect was found to be reversible and an2 value of −3 10−9 cm2/kW was measured.

Two-photon induced fabrication of gold microstructures in polystyrene sulfonate thin films using a ruthenium(II) dye as photoinitiator

Gold microstructures are produced with a femtosecond laser in thin films of a polystyrene sulfonate matrix containing gold ions. Two-photon induced metal reduction is obtained by addition of 0.1wt% of ruthenium(II)tris(bipyridine) in the formulation. Laser power is reduced to 5mW, thereby limiting thermal effects. Lines of typically 150nm heights and 1μm widths are fabricated as well as freestanding bidimensional structures. An additional electroless plating step produces gold structures with conductivities only ten times smaller than the bulk metal.

Optical control of an integrated interferometer using a photochromic polymer

An integrated optical interferometer has been fabricated using ion exchange technology in glass. Using a photochromic polymer, we show that it is possible to reversibly modulate the phase of the guided wave with an optical control beam. This constitutes a demonstrator of an optically controlled integrated optical device.

PREPARATION AND CHARACTERIZATION OF HGXCD1-XS AND PBXCD1-XS QUANTUM DOTS AND DOPED THIN FILMS

Thin silica and silica-titania films doped with sulfide nanocrystals of controlled size were fabricated by a method based on the preparation of colloidal particles and their introduction into a glassy matrix through the sol-gel method. Colloidal sols of composition HgxCd1-xS and PbxCd1-xS (with x ranging from 0 to 1) were prepared and used to dope alkoxide solutions for the deposition of thin silica and silica-titania films. Optical absorption spectra were taken on both precursor colloidal sols and derived doped films. X-ray diffraction characterization gave structural information on the nature and size of particles in powders obtained by precipitation from colloidal sols and in doped films. The advantages and limits of the investigated systems are discussed in light of possible applications. The nonlinear properties of the most interesting PbS-doped planar waveguides have been investigated in the near-infrared, at 1.064 μm. A reversible nonlinear effect was measured, with n2 values ranging from -5 to -20×10-9 cm2/kW.

Stable dual-wavelength microlaser controlled by the output mirror tilt angle

A continuous-wave dual-wavelength solid-state microlaser is presented and a technique for regulating the gain competition between the two wavelengths is proposed, based on the angular tilt of the laser cavity output mirror. Laser behavior is studied and balanced dual-wavelength emission is obtained with output power levels as high as 200 mW for 2 W pump power. Sum frequency mixing is demonstrated making the source promising for Terahertz generation in the 0.5-0.7 THz range through difference frequency generation.

Sol - gel glasses for nonlinear optics

In recent years a large amount of activity has been carried out searching for novel or advanced materials which exhibit large nonlinear third-order susceptibility . Emphasis has been put on materials suitable for integrated optical circuits, since the guided-wave format can provide additional routes to the conception and realization of photonic devices. The preparation of nanoparticle-doped glass by the sol - gel technique represents one of the most promising approaches: here we give a short overview of alternative processes to control the size of semiconductor clusters and we present experimental results from CdS- and PbS-doped silica - titania sol - gel films.

Feasibility of optically controlled integrated Mach–Zehnder device based on Azo dye-doped PMMA thin films

Azoaromatic (Azo) polymers have attracted much attention as materials for nonlinear and optoelectronic applications. In this work, nonlinear properties of the concerned material are first characterized by m-lines spectroscopic method. Then, photoinduced phenomena reported in the literature are summarized and experimentally found out. Therefore, these photoinduced properties are used to design and manufacture an optically controlled integrated device based on light wave intensity dependence of refractive index.

Optical parametric amplification in composite polymer/ion exchanged planar waveguide

A simple hybrid polymer/ion exchanged planar optical waveguiding structure has been fabricated which allows us to realize phase matching between different guided modes without any corrugation or modulation of the structure. A nonlinear polymer is deposited on top of glass substrate with a waveguide realized by the ion-exchange technique. Efficient optical parametric amplification is demonstrated for a pump at 532 nm and a signal at 814 nm. A 1 dB internal optical gain is achieved after propagation on 5 mm, with a pump power of 15 kW/mm.

Modal dispersion phase-matched frequency doubling in composite planar waveguide using ion-exchanged glass and optically nonlinear poled polymer

Abstract We report on the fabrication and characterization of composite planar waveguides for frequency doubling. Modal dispersion phase matching is obtained for TM 0 fundamental and (TM 1 , TM 2 ) harmonic wavelength. The experimental conversion efficiency was η =0.45% with an SH wavelength of 0.516 μm for TM 0 ω –TM 2 2 ω mode conversion. The phase-matching condition can be fulfilled by adjusting the diffusion time of ion-exchange and the thickness of the polymer layer.

Grating and prism couplers: radiation pattern and m-line

Abstract Prism or grating couplers are known to exhibit m-lines in the far-field and zeros in the near-field. Despite the fact that a lot of papers have been devoted to these couplers, there is some confusion concerning the possible link between the m-line and zero: is the former a consequence of the latter? One of the objects of this paper is to clarify this point. It is the opportunity to consider, in addition to the near-field and far-field patterns, the question of the intermediate region constituted by the Fresnel zone and to give a criterium of the far-field pattern.