Thin film coating techniques appear to have many advantages over other techniques for immobilization and incorporation of chemical indicators to optical waveguides in developing dye based fiber optic chemical sensors. We have fabricated thin films of composites by using sol-gel and RF sputtering techniques. Different organic and inorganic indicators were immobilized in these films and incorporated into optical waveguides for sensor applications. A fiber optic pH sensor has been developed by introducing pH indicators into a silica matrix and coated as a thin film onto a porous glass fiber by a sol-gel technique. Also, a hydrogen gas fiber optic sensor has been developed by using a RF sputtered WO3/Pd coated porous optical fiber.

In Integrated Optics (10), LiNbO3 is a well known material, widely used to realize very efficient electro-optic integrated devices for telecommunications such as phase modulators, intensity modulators and directional couplers. But, with the availability of good quality rare earth doped material and the perfecting of a new waveguide fabrication technique, Proton Exchange (PE), a completely different set of active devices are now possible. The common factor of these devices is that they take advantage of the high optical power resistance of the PE waveguides, of the amplification due to the rare earths, and, of the electro-optic/nonlinear properties of the crystal. In this paper we shall present such devices we have demonstrated in collaboration with the Central Research Laboratory of Thomson CSF and the Ecole Nationale Supérieure de Physique de Marseille.:

-an optically pumped CW amplifier in Nd:MgO:LiNbO3 offering up to 8 dB small signal gain at δ = 1.085μm

-an optically pumped CW laser in Nd:MgO:LiNbO3 emitting 14 mW at X = 1.085μm with a slope efficiency of 34% and a threshold of 2.7 mW

-an FM Mode-locked waveguide laser in Nd:MgO:LiNbO3 realized by electro-optically driving the laser at the cavity round-trip frequency emitting 8 ps pulses of 250 mW peak power with a 6.2 GHz repetition rate

-a self doubled waveguide laser in Nd:MgO:LiNbO3 emitting some hundreds of μW in the blue (SHG of the pump and mixing the pump with the laser frequency) and the green (SHG of the laser wavelength).

Ion-beam/channeling data for the lattice location of Ti, Hf, Er and Nd in LiNbO3 and LiNbO3: Mg are presented. These impurities are relevant in relation to waveguide and integrated optics devices. It is shown that co-doping with Mg markedly influences the lattice location observed in LiNbO3. The amorphization and recrystalization process following Hf implantation and annealing are also discussed.

With proton exchange on LiNbO3 or LiTaO3 it is possible to fabricate waveguides presenting simultaneous modulation of the refractive indices and nonlinear coefficients. This allows us to realize a new kind of Quasi Phase Matching, and we will describe the first experimental results.

Optical planar waveguides, with a controllable thickness in a very wide range, typically from 3 to 20 μm, can be fabricated by thermally controlled proton implantation in LiNbO3. In the nuclear stopping region at the end of the ion's tracks a sufficient decrease in refractive index is obtained, thus forming an adequate optical barrier. The mode confinement was investigated by dark line mode spectroscopy, and the refractive index profiles were reconstructed. The effects of different ion fluences and ion energies in the Mev range on the refractive index profile at 300 K have been investigated.

Single crystals of KNbO3 have an excellent potential for integrated and nonlinear optical applications. MeV He ion implantation is a reliable technique for the formation of permanent optical waveguides in this material. We have fabricated planar and strip waveguides using He energies between 1 and 3.5 MeV and ion doses of 5 × 1013 to 1016 ions/cm2. Waveguides were analyzed at a wavelength of 514, 633 and 860 nm.

TiO2-B2O3 doped silica single-mode waveguide arrays on silicon substrates were fabricated by flame hydrolysis soot deposition, glass consolidation and etching. CHF3 reactive ion etching is suitable for more than 15 μm deep vertical gap and reflector preparation. Minimum waveguide propagation loss values of (0.21±0.01) dB/cm were measured on 50 mm single-mode samples. Spectral measurements proved the absence OH absorption in the 850 to 1600 nm range and indicate scattering as the most important loss effect.

The success of photonic switching depends on the development of materials capable of processing light signals without the interweaving conversion to electronic signals. The photodeposition of metal oxides onto porous Vycor glass and silica glass sol-gels produce changes in the index of refraction of the glass of the order of 0.1 to 0.001. Nonlinearities in transmission and refractive index allow the deposition of 1.0-10.0 μm width planar waveguides with attenuations of 0.6 dB/cm. This technique is being evaluated for the optical performance of couplers, dividers, and interferometers. Also 3-dimmensional interactive planar waveguide structures are being fabricated in silica sol-gel thin-films.

The realization of single-mode rib-waveguides with dimensions of several micrometers in Silicon-On-Insulator (SOI) is reported. The predicted monomode behaviour is confirmed by comparison of a simulated and a measured nearfield intensity distribution. Waveguide losses below 0.5dB/cm were obtained at wavelengths of 1.3μm and 1.55μm, respectively, independent of the polarization state.

During the recent years, a great variety of ion-exchange processes, including one-step or two-step electric field assisted ion-exchange processes, have been developed to fabricate different kinds of passive planar glass waveguides, e.g., surface waveguides, which correspond to surface maximum concentration, or buried waveguides, which correspond to inside maximum concentration [1,2,3]. Theoretical calculation of ionic concentration distribution has been of interest since refractive index is generally a linear function of concentration. A general analytical solution to calculate both surface and buried concentration distributions from different ion-exchange processes, however, has not yet been presented. In addition, traditional ion-exchange has been carried out only with constant surface concentration boundary conditions. Little attention has been paid, either experimentally or theoretically, to ion-exchange processes with variable boundary conditions. In fact, the time-dependent surface concentration is experimentally observed for the ion-exchange of GRIN glass in molten salt bath [4]. Very recently, a novel one-step technique [5,6] involving electric field assisted ion-exchange of Na+ in glass by Ag+ from molten AgNO3 bath with decaying silver concentration has been developed to produce buried Ag+ concentration profiles in glass. As the accurate and reproducible processes are very important for fabricating ion-exchanged glass waveguides, theoretical modeling and analysis on the new process are needed.

In this paper, the one-dimensional field-assisted linear diffusion equation has been analytically solved by Laplace transformation to theoretically calculate concentration profiles produced by field enhanced ion-exchange process with exponentially decaying surface concentration boundary conditions. The applications of the solution to a variety of ion-exchange processes with different boundary or processing conditions for optical waveguide fabrication have been discussed. The theoretical results prove that the solution is a general analytical solution which can be used to calculate either surface concentration profiles or buried concentration profiles.

X-ray absorption and Mossbauer spectroscopy were used to study chemical and magnetic properties of photodeposited Fe in Porous Vycor Glass(PVG). Extended X-ray Absorption Fine Structure(EXAFS) measurements of Fe samples show that after photolyzation, the Fe atoms are surrounded by two shells of six oxygen atoms and eight Fe atoms. The Fe-O and Fe-Fe distances are 1.84 °A and 1.99 °A respectively. After heating to 650 °C and 1200 °C shortening of bond lengths are observed. The second shell of Fe in unheated and heated to 650 °C samples have Fe-Fe distances of 3.0 °A and 2.98 °A respectively. Samples consolidated at 1200 °C show the Fe atoms to be surrounded by two shells of Fe atoms at 2.86 and 3.03 °A. This data together with Mossbauer and XANES spectra suggest that Fe exists in two different configrations, one is an Fe-Fe compound and the other is an octahedral Fe oxide similar to Fe2O3.

We have embedded nm-size Cu clusters in optically dense, thin (∼ 150 nm) layers using standard ion implantation techniques. The size and size distribution of the clusters can be altered by varying such ion-implantation parameters as total dose and current density. The layers exhibit both a thermo-optic and an electronic nonlinear optical response, depending on the mode of laser excitation. The electronic nonlinearity has a response time no longer than 5 ps.

Multi-energy nitrogen implantation into thermally grown SiO2 on silicon substrates has been performed and the optical wave-guiding properties of this structure has been studied. The implantation energy used was in Ie range of 40 KeV to 150 keV, and the doses used were typically 2×1016 to 2×10−2. The energies and doses were chosen to achieve relatively flat implanted nitrogen profiles. It is found that optical waveguides can be formed when the implanted nitrogen concentration is sufficiently high. Both prism-coupling technique and end-fire coupling technique were used to test the implanted waveguides fabricated. Many m-lines including dark modes were observed by the prism-coupling method. This structure is found to be very stable against thermal annealing and there is no significant change observed in the waveguiding properties even after annealing at 1000 °C for four hours. The waveguide loss was found to be typically 0.6 dB/cm before annealing and can be further reduced to about 0.3 dB/cm after annealing.

Amorphous SiO2 films, 10 μm thick, were grown on Si(100) substrates and subsequently implanted with 5.0×1015 Er ions/cm2 at an energy of 3.5 MeV. When optically pumped at λ = 488 nm, the implanted films show a sharply peaked photoluminescence spectrum centred around λ. = 1.54 μm, corresponding to an intra-4f transition of Er3+. Thermal treatment at temperatures above 700 °C is needed to anneal out the implantation-induced defects and attain a maximum PL intensity and luminescence lifetime (15 ms). Extended x-ray absorption fine structure (EXAFS) spectra of Er-implanted bulk silica samples (3.4×1016 ions/cm2, 2.9 MeV) indicate that the Er has six O first neighbours at a distance around 2.25 Å. The results are similar to those for bulk samples doped with Er in the molten phase.

Results are presented for the propagation loss of planar optical waveguides fabricated in SIMOX structures with Si overlayers whose thickness varies from 0.57 μm to 6.0 μm. The results demonstrate that thick Si overlayers are required to produce propagation losses below 1 dB/cm. In addition, the results of the coupling between two vertically integrated waveguides formed using two buried SiO2 layers are also reported.