Because of the low dimensional power of its force scaling law, surface tension is appropriate for carrying out reshaping and assembly in the microstructure size domain. This paper reviews work on surface tension powered self-assembly of microstructures. The existing theoretical approaches for rotational assembly are unified. The demonstrated fabrication processes are compared. Mechanisms for accurately determining the assembled shape are discussed, and the limits on accuracy and structural distortion are considered. Applications in optics, electronics and mechanics are described. More complex operations (including the combination of self-assembly and self-organization) are also reviewed.

Surface tension-powered self-assembly of microstructures - the state-of-the-art

Methods are provided for forming optical devices, such as waveguides, with minimal defect formation. In one aspect, the invention provides a method for forming a waveguide structure on a substrate surface including forming a cladding layer on the substrate surface, forming a core layer on the cladding layer, depositing an amorphous carbon hardmask on the core layer, forming a patterned photoresist layer on the amorphous carbon hardmask, etching the amorphous carbon hardmask, and etching the core material.

Use of amorphous carbon film as a hardmask in the fabrication of optical waveguides

Molecular beam epitaxy (MBE)-grown bulk and short-period superlattices of (Al,Ga,In)As epilayers lattice matched to InP were characterized by double-crystal diffractometry and low-temperature photoluminescence. A reflection spectroscopy technique was used to determine the refractive index of (Al,Ga,In)As films as a function of wavelength. The measured data were fitted to a single-oscillator dispersion model, and the model coefficients are given. The resulting expression can be used in the design of waveguides, modulators, and other optical devices. >

Refractive indexes of (Al,Ga,In)As epilayers on InP for optoelectronic applications

An optoelectronic transceiver module is described consisting of a four-channel AlGaAs integrated laser/monitor transmitter and a four-channel GaAs MESFET integrated detector/preamp receiver. The optoelectronic chips are flip-chip, solder-bump bonded to a substrate containing electrical wiring and planar-processed optical waveguides. The optical waveguide layer serves two purposes: the routing of optical signals, as well providing mechanical registrations for the optoelectronic chips and fiber-optic ribbon connector. The work described here demonstrates one approach to high-density, optoelectronic array packaging compatible with existing high-performance electronic packaging technology. >

A high-density, four-channel, OEIC transceiver module utilizing planar-processed optical waveguides and flip-chip, solder-bump technology

Provided are methods of forming optical waveguides. The methods involve: (a) forming over a substrate a layer of a photodefinable composition; (b) exposing a portion of the layer to actinic radiation; (c) developing the exposed layer to form a waveguide core structure; and (d) heating the waveguide core structure to a temperature and for a time effective to reflow the structure such that it becomes at least partially rounded in cross-section. Also provided are optical waveguides formed from the described methods and electronic devices including one or more of the optical waveguides.

Methods of forming waveguides and waveguides formed therefrom

A technique for fabricating silica channel waveguides with circular cross sections is presented. The geometrical mismatch between a square or rectangular waveguide and a regular optical fiber is therefore largely reduced. The fiber-waveguide-fiber coupling loss drops from 1.8 dB to 0.5 dB or less for step index multimode waveguides by applying this technique. The heat treatment applied in the waveguide rounding process also smooths the waveguide sidewalls and results in much lower propagation loss in the waveguides. Uniform Y splitters were fabricated to show the feasibility of using this technique to make integrated optical devices. >

Silica-based circular cross-sectioned channel waveguides

High-silica optical waveguides are fabricated on alumina substrates by flame hydrolysis deposition (FHD) and reactive ion etching (RIE) patterning techniques. The composition of the high-silica glass waveguides is adjusted from that of the conventional FHD glass to reduce the thermal expansion mismatch between silica glass and alumina. Glass waveguides made in this way exhibit low loss and are compatible with various types of alumina ceramic substrates. >

W.M. Myers

Papers

Silica-based circular cross-sectioned channel waveguides

High silica waveguides on alumina substrates for hybrid optoelectronic integration