A. Loni

Novel liquid sensor based on porous silicon optical waveguides

The introduction of solvents into the pores of optical waveguides formed using porous silicon is shown to dramatically reduce the interfacial scattering loss of the waveguides (by as much as 34-dB cm/sup -1/ in one example), in a reversible manner. The degree of loss reduction is dependent on the type of solvent introduced. These observations, combined with the fact that a substantial portion of the guided-mode field interacts with the solvent introduced into the pores, indicate that an enhanced sensitivity for sensor applications may be achievable across a broad range of operational wavelengths.

The application of porous silicon to optical waveguiding technology

The porosification of silicon can be achieved by the partial electrochemical dissolution (anodization) of the surface of a silicon wafer. The degree of porosity is dependent on the anodization parameters and can generally be controlled within the constraints imposed by substrate dopant type and concentration. Control of porosity leads to control of refractive index, and therein lies the concept of using porous silicon as an optical waveguide. We discuss porous silicon wavegides, for the visible to the infrared, produced by a number of approaches: 1) epitaxial growth onto porous silicon (where the porous layer acts as a substrate for a higher refractive index waveguide epilayer); 2) ion implantation (where either selective areas of high electrical resistivity can be produced, which act as a barrier against porosification, or where the surface of a porosified layer is amorphised to form a waveguide; 3) porous silicon multilayers (where the anodization parameters are periodically varied to produce alternate layers of different porosity and thus refractive index); and 4) oxidation of porous silicon (where a porosified layer is oxidized to form a graded-index, dense or porous, oxide waveguide).

Progress towards achieving integrated circuit functionality using porous silicon optoelectronic components

Porous silicon offers many potential advantages for the realisation of optoelectronic circuits and systems. This paper assesses some of the technologies available for the fabrication of porous silicon waveguides for visible and infrared applications. The unique physical and chemical properties of the material enable additional functionality over other silicon-based optoelectronic technologies. As an example, optical sensing of solvents and vapours is discussed using both optical waveguides and multi-layer reflector stacks.

Novel glass compositions and fabrication technologies for photonic integrated circuits

Heavy metal fluoride, chalcogenide, and fluoro-tellurite glasses proffer photonic integrated circuit functionality over a wide wavelength range, and combine high optical non-linearity with the ability to incorporate active dopants. The ability to access a range of glass compositions offers great flexibility in both design and processing. In this paper, we present fabrication methodologies for producing such novel glass-based waveguide components.

Large core, single-mode glass-based waveguides for photonic integrated circuits

We previously demonstrated light guiding in fiber-on-glass (FOG) dielectric waveguides using fluoro-tellurite glasses. These waveguides were fabricated by mechanically pressing a fiber onto a polished planar glass substrate of lower refractive index above the glass transition temperatures. However, two handling constraints have been discovered in this approach. In practice, for novel inorganic compound glasses, the minimum dimension of fiber that can be handled is preferably around 30μm. The minimum refractive index difference between the fiber and the substrate that can be reliably achieved at present with these glasses is 0.01. Our simulation results showed that, taken together, these restrictions provide a practical barrier to achieving single-mode FOG operation at telecommunications wavelengths. Here we present simulation and experimental results for a new inorganic glass FOG waveguide that simultaneously meets these handling constraints and achieves mono-mode operation around 1.55 μm. In this new design, a homogeneous glass fiber is partially embedded lengthwise in a substrate of higher refractive index glass; the nonembedded part of the fiber is air clad. Simulation results presented for fluoro-tellurite FOG waveguides confirm the success of the new design in realizing single-mode propagation at 1.55 μm for a fiber diameter of 30 μm and a fibersubstrate refractive index difference of 0.01. The design is robust, with good dimensional fabrication tolerance, but predicted losses are over 6 dBcm-1. A proof-of-principle demonstrator is fabricated using two commercially available multi-component silicate glasses (Schott F2 and F4). This shows multimode waveguiding at 0.633 μm, guidance around a curve, and appears mono-mode at 1.575 μm.

Review: fine embossing of novel glasses for photonic integrated circuits

Hot embossing of novel inorganic-compound glasses is a new fabrication technology for guided wave devices and circuitry. A patterned mould is pressed into the glass above its glass transition temperature (Tg) and replicated; cooling below Tg freezes-in the required pattern. The state-of-the-art is reviewed. Better than 0.1 μm -scale replication is shown for chalcogenide glasses and fabrication of a hot embossed monomode waveguide demonstrated.

Review: Fine Embossing of Novel Glasses for Photonic Integrated Circuits

Hot embossing of novel inorganic-compound glasses is a new fabrication technology for guided wave devices and circuitry. A patterned mould is pressed into the glass above its glass transition temperature (Tg) and replicated; cooling below Tg freezes-in the required pattern. The state-of-the-art is reviewed. Better than 0.1 mum-scale replication is shown for chalcogenide glasses and fabrication of a hot embossed monomode waveguide demonstrated.