Diffraction Management in Waveguide Arrays

Arash Joushaghani

The Edward S. Rogers Sr. Department of Electrical and Computer Engineering (Photonics)

Abstract:

Electromagnetic waves tend to broaden in time and space as they propagate. The temporal broadening is due to dispersion, caused by the dependence of the materials permittivity on the frequency of the light. The spatial broadening of a pulse is due to diffraction, and happens because all spatially finite waves have wave vectors perpendicular to their propagation direction.
Dispersion is zero in vacuum and in different materials can be have different signs. Hence the effects of dispersion can be cancelled by using materials with alternating signs of dispersion. No such analogy exists for diffraction. As a result we can not engineer diffractive properties of systems as we tailor its dispersive properties.
In this talk we explore a new diffraction scheme known as discrete diffraction which occurs in waveguide arrays and can be engineered and controlled. By tailoring the geometry of our waveguide arrays, we can control the rate and the sign of diffraction. This diffraction management schemes enables us to use diffraction to our advantage and engineer devices that benefit from it. For example, in optical amplifiers, diffraction control can allow us to spread a pulse in space and reduce its peak intensity, there by avoiding saturation effects.

 

Biography:

Arash Joushaghani is a first year PhD student at the University of Toronto. He is currently supervised with Stewart Aitchison and Joyce Poon and is researching on the ultrafast dynamics of plasmonic waves. He obtained his Bachelors' degree at the University of Toronto at Nanoengineering, Engineering Science at 2008.