The Berini Group

 

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Research: Integrated optics based on surface plasmons (NSERC)

This research program is devoted to the study of integrated optic elements based on waveguides comprised of a thin narrow metal film buried within a dielectric. Such waveguides were recently discovered to support a long-range (low-loss) surface plasmon-polariton (LRSPP) wave having a field profile that is amenable to end excitation using an optical fibre. The main objective of this project is to establish this integrated optics technology, which means developing models from first principles for all of the main passive elements required (straight waveguides, bends, S-bends, Y-junctions, couplers, Mach-Zehnder and multi-mode interferometers, multi-mode and Bragg gratings) and validating the models experimentally. The scientific approach thus comprises a mix of theory and experiment appropriate to meeting the main objective. All theoretical models will be based on first principles and developed from rigorous electromagnetic field theory. Since commercial CAD tools cannot handle these 3D structures, numerical techniques will be applied to solve the governing differential equations. Experiments will be defined and conducted to verify and validate all models proposed. Appropriate experimentation vehicles consist of thin gold features deposited on a glass substrate, covered with index matched gel, and designed for operation at the free space optical wavelengths of 633, 1310 and 1550 nm. The rationale for this experimental framework is that the structures can be fabricated cheaply using standard semiconductor fabrication tools and techniques, and the wavelengths are easily accessible using inexpensive lasers, optoelectronics and optics.


 

Measured output intensity distribution at l0 = 1550 nm for various passive elements operating in the LRSPP mode for an Au stripe 8 mm wide and 20 nm thick in SiO2. (a) Mosaic of outputs for a series of couplers where the spacing between the parallel stripes is varied. (b) Output of a straight waveguide. (c) Output of an S-bend. (d) Output of a Y-junction splitter. (e) Output of a Mach-Zehnder interferometer. (f) Output of sharp angle bends. (g) Output of a Bragg grating implemented as a step-in-width structure. (Refs. J19, J23 under Publications.)