Todd Ryan Tolliver

Magnetic resonance imaging, a commercial application for analog photonics

Replacing coax bundles in magnetic resonance imaging systems with fiber eliminates many problems such as crosstalk, ground loops, EMI, and safety hazards. An analog photonic link has been demonstrated with excellent image quality.

A self-forming compact polymer waveguide for efficient chip-to-chip single-mode interconnection based on radiation mode coupling

Based on radiation mode coupling through a self-formed polymer waveguide extension, efficient single-mode optical coupling can be achieved between the active and passive chips while relaxing the stringent positioning requirements. A 20 dB improvement can be achieved according to simulation results.

Selective Area Heteroepitaxy of Nano-AlGaN UV Excitation Sources for Biofluorescence Application

We report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters; including temperature, pressure, NH3 flow, total alkyl flow and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant which resulted in a high quality pyramidal structure. As indicated by high resolution x-ray diffraction (XRD) and cathodoluminescence (CL) spectroscopy, composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.

Toward multifunctional optical integration: an adaptive lithographic method for patterning optical structures

A new method of interconnecting various optoelectronic components is discussed. Offset error up to 25 microns can be corrected to achieve single mode alignment accuracies. Several planar optical devices were photocomposed using the adaptive photolithographic method and these have been shown to perform with the desired characteristics.

A polymer-based platform technology for integrated photonics

Polymers have been studied as an alternate material to silica for optical interconnects and photonic devices for the last decade. In this paper we review the work performed at GE Global Research in the area of polymer based material systems for photonic applications. A description of the application of the technology to several different areas is presented. Some of these application areas include optical interconnects, optoelectronic integration and electro-optical devices using polymer material systems. The overall effort includes areas of research from the basic chemistry of polymer optical materials to the development of photonic components. Specifically the use of polymer materials as a platform technology for hybrid integration in the development of multi-functional sub systems is reviewed.

a-Si/c-Si interfaces: The effect of annealing and film thickness

Very thin intrinsic amorphous silicon films (≪10 nm) are used for passivation studies of crystalline silicon. In this paper, a-Si:H layers are subjected to a variety of post-treatments. A hydrogen plasma treatment crystallizes the thin film almost instantaneously, significantly reducing the effective lifetime. Anneals in different atmospheres typically show similar results, which are highly dependent on the initial state of the a-Si/c-Si interface. Data will be discussed and conditions compared of thin intrinsic a-Si:H films that show changes in effective lifetime due to annealing. Films with initial low effective lifetimes can result in low or high lifetimes after annealing, while the opposite is also possible; films with high initial lifetime can result in low or high lifetime after annealing. Lastly, a minimum thickness of the intrinsic layer is needed for annealing to demonstrate a positive effect on the effective lifetime.

Radiation mode coupling between active and passive chips based on a self-formed compact polymer interconnect for single-mode chip-to-chip optoelectronic integration

Based on radiation mode coupling through a self-formed polymer waveguide extension, efficient single-mode optical coupling can be achieved between active and passive chips while relaxing the stringent positioning requirements. A 20dB improvement can be achieved according to simulation results. Single-mode waveguides have been successfully demonstrated using GE photo-definable polymer materials.

High-density multimode photonic backplane

The development of a photonic backplane for high-speed and high-bandwidth communications is presented. This hybrid, multimode, multi-channel backplane structure contains both electrical and optical interconnects, suitable for next-generation high-speed servers with terabit backplane capacity. Removable and all-passively aligned high density interconnects on this backplane are achieved by polymer based optical waveguides with integrated micro-optics and VCSEL arrays on conventional printed circuit boards. The fabrication of this photonic backplane requires few additional steps outside a traditional board-manufacturing environment and is largely compatible with existing processes.