W. J. Pan

Embossing of chalcogenide glasses: monomode rib optical waveguides in evaporated thin films

Single-mode optical rib waveguides operating at telecommunication wavelengths are successfully patterned via a hot embossing technique in a thermally evaporated chalcogenide glass thin film on a chalcogenide glass substrate. Ellipsometry is used to measure the refractive index dispersion of the pressed film (As(40)Se(60)) and substrate (Ge(17)As(18)Se(65)).

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: Tg - reversible glass door to fabrication of photonic devices and integrated circuits

We review our development of sub-micron hot embossing or imprinting of glasses. We suggest that this is an emerging technology which shows great promise for the fabrication of glass photonic integrated circuits (PICs). The approach makes use of Tg (the glass transition) which gives inorganic compound glasses a key advantage over crystalline materials for fabricating photonic devices and PICs. Thus, when a glass is heated above Tg, the glass transforms to a supercooled liquid which may be shaped e.g. moulded. Cooling back down through Tg allows the shaping to be retained in the glassy state at room temperature. In this way, glasses may be shaped from the macro-scale e.g. to make light-refracting lenses down to the nano-scale e.g. for waveguides or photonic crystal arrays for dispersion management. Hence Tg is a reversible door to making photonic devices. This claim is illustrated by reviewing our recent work on hot embossing of inorganic compound glasses to make waveguides. Opportunities and potential pitfalls are highlighted. The background understanding of glass science underpinning the hot embossing methodology is presented.

T g : The glass door to photonic devices and integrated circuits

An emerging technology which shows promise for the fabrication of glass photonic integrated circuits (PICs), is sub-micron-scale embossing or imprinting. This approach makes use of Tg (the glass transition) which gives inorganic compound glasses a key advantage over crystalline materials for fabricating photonic devices and PICs. Thus, on heating the glass above Tg the supercooled liquid temperature regime is accessed which enables shaping, e.g. moulding, to be carried out. Cooling back down through Tg allows the shaping to be retained in the glassy state. In this way, glasses may be shaped from the macro-scale e.g. to make light-refracting lenses down to the nano-scale e.g. for waveguides or photonic crystal arrays for dispersion management. Hence Tg is one door to making photonic devices. This claim will be illustrated by reviewing both the background methodology and our recent work on hot embossing of inorganic compound glasses to make waveguides. Opportunities and potential pitfalls will be highlighted.

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.