One of the most challenging applications of ferroelectric thin films is the formation of technologically practical optical waveguideing devices, particularly in the context of a dynamically changing environment where competing light sources and optical materials simultaneously undergo rapid improvement. In order to assess the prospects of this technology, a fundamental understanding of waveguide loss is being pieced together. This includes the relative contributions of surface scattering, and grain boundary scattering to optical losses. With computational models, it is possible to predict the surface losses from measured topographic data. This tool provides a method to probe the residual effects of grain boundaries, defects and impurities on optical losses. A comparative anatomy of various thin film structures and their loss characteristics will be provided in the context of these experiments.

Lithium niobate thin layers have potential applications in integrated, high efficiency signal modulators, and in second harmonic generation devices. We report the solution deposition of heteroepitaxial LiNbO3 thin layers on (006), (110) and (012) sapphire. Factors affecting surface roughness were investigated by atomic force microscopy. The best results for optical losses occurred after fresh, 0.1M unhydrolyzed solutions were used. Channel waveguides were developed by lithography and proton exchange. Waveguides were formed in Nd3+- and Er3+-doped thin layers to confine light and assess the possibility of integrated waveguide lasers.

Silica integrated optical circuits are expanding in functionality to include optically active waveguides. Traditionally, the planar optical waveguide structures include silica based glass films such as thermal oxides, phosphorous, and boron-phosphorous doped glasses. Various efforts have successfully doped conventional waveguides with Er, typically by solution doping. Material issues such as rare earth solubility and glass structure dictate that efficient optical amplifiers based on such waveguides have path lengths in excess of 10–15 cm. We have developed an alternative strategy using Er-doped soda-lime silicate glass films on silicon. The waveguide processing utilizes methods of deposition similar to those used in silicon IC technology, with modificatons in the compositions and thicknesses. In these glasses the effective solubility limits are relaxed and we have successfully fabricated short path length devices which demonstrate net gain of more than 4 dB/cm. Short path length devices offer a potential advantage in highly integrated multi-channel devices and offer an additional building block in system architectures.

This paper presents the results of our investigation into the possibility of increasing both the radiative cross-section and the electrical activation efficiency in erbium (Er3+) doped silicon (Si). The energy levels of the isolated Er3+ have been theoretically predicted, employing the Thomas-Fermi method. The behaviour of these levels in Si was then investigated using a Kronig-Penney approach. Initial theoretical results imply that fluorine (F), in addition to Er3+ in Si, increases the radiative cross-section of Er3+ by at least an order of magnitude, and that co-doping appears to enhance the mixing of the 4f and 5d levels and causes the Er3+ energy levels to overlap with those of the host. Photoluminescence spectra of Er3+ in Si co-doped with F also indicate an interaction with the host lattice which appears to be dependent on its electrical characteristics.

This paper reports a study of the non-radiative processes competing with the excitation of the erbium ion in layers implanted with high concentrations of erbium and oxygen. These processes reduce the luminescence efficiency of the Si:Er system and dramatically increase the threshold current density calculated to be necessary for an ultimate goal, the Si/Ge:Er LASER. Using cross sectional TEM, photoluminescence as a function of temperature and DLTS, it is demonstrated that a two stage anneal procedure which avoids the formation of extended defects and removes specific deep states is necessary to obtain efficient Er3+ excitation at high erbium concentrations. Comparisons are made with damage resulting from germanium implantation into silicon. The role of multiple stage anneals is discussed in relation to the removal of Shockley-Hall-Read recombination centres

The fabrication and optical properties of an erbium-doped gallium phosphide microdisk resonator pumped by a Ti-sapphire laser at 980 nm were investigated. Enhanced Er3+ intra-4f-shell photoluminescence was observed in the microdisk resonator compared to a thin film, and is attributed to a microcavity effect. At low pumping power intensity, the photoluminescence from erbium-doped gallium phosphide microdisks is an order of magnitude more intense than that from a thin film sample.

We have investigated the properties of rare earth-doped InGaAsP thin films with special interest in magneto-optical device applications. Magneto-optical properties have been used in optical systems as isolators, waveguides, and switches. These materials and devices can be used to expand the functionality of InP opto-electronic integrated circuits (OEICs). Thin films of InP, InGaAs, and InGaAsP, grown by liquid phase epitaxy, were lattice matched to the (100) InP substrates. The films were n-type, with the carrier concentration decreasing by an order of magnitude in the doped films due to gettering by the rare earth elements. The doped films contained 2.6×1018 - 1.5×1020 cm−3 rare earth elements, which were observed to segregate toward the film/melt interface in the more highly doped films. A broad photoluminescence was observed at 1.52 μm in the Er-doped films. The Verdet constant was measured through the sample thickness, and the substrate signal dominated the measurements. However, the measured values were in agreement with published values for InP, which gives an indication of the films' host value. The Verdet constants increased from 4 to 7 deg/T/mm as the wavelength decreased toward the band edge. The band edges of our samples were 0.93, 1.62, and 1.30 μm, respectively. Rare earth dopants were observed to raise the refractive index of the InP films, and waveguiding at 1.3 μm was achieved in the rare earth-doped InP films and in the InGaAsP films.

We describe a novel means for the production of optically active planar waveguides. The technique makes use of a low energy plasma deposition. Cathodic-arc-produced metal plasmas are used for the metallic components of the films and gases are added to form compound films. Here we discuss the synthesis of A12-xErxO3 thin films. The erbium concentration (x) can vary from 0 to 100% and the thickness of the film can be from Angstroms to microns. In such material, at high active center concentration (x=l% to 20%), erbium ions give rise to room temperature 1.53μm emission which has minimum loss in silica-based optical fibers. With this technique, multilayer integrated planar waveguide structures can be grown, such as Al2O3/Al2-xErO3/A12O3/Si, for example.

Calcium fluoride thin films grown on silicon substrates by sublimation under ultra high vacuum are well known to be highly efficient hosts for rare earth luminescence properties. For this reason we incorporate erbium by ion implantation in order to form optoelectronic integrated devices. Here we describe the incorporation conditions of erbium in CaF2/Si structures and their luminescence characteristics. The properties of the material have been investigated for implantation doses varying from 4×1014 to 1×1017 at.cm−2. The role of oxygen in the charge compensation mechanisms is investigated and it is shown that the maximum emission in erbium at 1.53μm occurs for an implanted dose of 2×1016 at.cm−2. This corresponds to an Er concentration three orders of magnitude greater than for the case of classical-erbium-doped semiconductors. At this high concentration (up to 15 at.%) the light emission mechanisms are of great theoretical interest. They involve strong Er-Er coupling effects: energy transfer, cross-relaxation phenomena and high conversion efficiencies.

These properties make erbium-implanted CaF2/Si structures excellent candidates for the production of optically active waveguides. The guiding structure can be formed by high energy implantation to build a buried active region of high refractive index within the CaF2 thin film.

The implantation of MeV Ge3+ ions into fused silica has been used to fabricate single mode channel waveguides with a low propagation loss of 0.10–0.15 dB/cm. The loss coefficient, α, has been measured as a function of ion dose (8 × 1013 to 8 × 1016 ions/cm2) and annealing temperature (250 to 600 °C) at λ = 1300 nm. The value of cc for the as-implanted waveguides exhibited a minimum of -1.0 dB/cm at an intermediate range of dose from 8 × 1014 to 8 × 1015 ions/cm2. A progressive reduction in α occurred as the annealing temperature was increased from 300 to 500 °C. Annealing of the implanted waveguides at 500 °C for 1 h has produced an order of magnitude decrease in α to 0.1 dB/cm at 8 × 1014 ions/cm2. At doses which were outside of the intermediate range, the value of α was ≥ 10 dB/cm. This trend in α with ion dose has been attributed to the dominance of a residual nuclear component of damage after annealing.

The evolution of second harmonic generation (SHG) in germanium doped silica planar waveguides is simulated numerically. Based on the asymmetric photoionization model, the total current in the waveguide is taken to be the sum of an asymmetric current and a current due to the resulting dc field. The interplay between these two currents causes the SHG to saturate in time. The saturation of SHG in length is due to diffraction.

High-dose ion implantation was used to create silver metallic grains in the epoxy resins The structure and optical properties of Ag/organic systems were investigated by transmission electron microscopy and absorption UV-visible spectroscopy, It was established that silver implantation into the organic substrate produced colloidal nanoclusters in the near-surface region, whose average size and size distribution were function of dose value. The silver nanoclusters give rise to optical absorption at the plasmon wavelength. and maximum absorption was shown to be correlated with filling factors. The d.c. resistivities of irradiated samples were measured in temperature range from 5 to 300 K The observed exp(T0/T)n behaviour of resistivity indicated that synthesized metal particles are separated.

Thin films of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) were prepared by sol-gel technique and deposited on platinum coated-silicon wafer. The thicknesses of the two films were ∼400 nm and ∼550 nm, respectively. Micro-Raman spectra of the PMN-PT films show strong broad bands centered at 50, 136, 276, 450, 510, 556, and 790 cm−1, which are characteristic of PMN formation. Temperature dependent Raman scattering from 290K to 70K did not show any significant change in the bandwidth of the peaks, meaning thereby that the relaxation times of these phonons are practically temperature independent. The bands are interpreted as due to a break down in the phonon momentum conservation within the Brillouin zone, which is associated with some degree of disorder in the material. As a result, the Raman spectrum is a weighted average of the density of phonon states. Micro-Raman measurements in many different places on the films clearly indicate that they are homogeneous. In addition, the differences found in the Raman spectra of the films, particularly the band at 790 cm−1 is discussed. FT-1R measurements of the PMN-PT films present two broad bands around 260 and 550 cm−1, which are characteristic of perovskite structure and are primarily due to motions of oxygen ions. Also, these bands are compared with those found in PMN single crystal, and with those found in other similar systems, such as PLZT and PSN. SEM and XRD techniques have been used for the structural characterization.

Lead lanthanum titanate ((Pb1−x/100Lax)Ti1−x/400O3, x=10, 20, 28) sol-gel thin films were prepared on SiO2/Si and glass substrates using lanthanum nitrate as a La precursor. The effect of the processing conditions was investigated and the optical properties of the films were measured to obtain good films for waveguide applications. The perovskite crystalline phase is achieved regardless of the heating condition but the slower heating creates better quality films. La content in the film does not effect on the refractive index and transparency of the film.