Seminar - Sahar Sargheini

Speaker

Sahar Sargheini, PhD Candidate, ETH Zurich, Switzerland

Abstract

Plasmonic nano particles play a very significant role in the field of optics. Because of their small size and material properties, highly localized fields can be obtained. Thanks to advances in manufacturing methods, plasmon resonances have found many applications such as second harmonic generation and sensors. However, they have not yet been very successful in commercialization due to losses and high sensitivity of plasmonic resonances to fabrication based perturbations. Nano particles are always subjected to defects which can significantly affect their behavior. Thus, it is important to know how sensitive is the performance of the particle to changes in the shape. This is achieved through shape sensitivity analysis which is based on evaluating the shape gradient of the output functional with respect to the shape. Shape functionals in electromagnetic problems, e.g. the far-field pattern, depend on the shape of the domain and are constrained by Maxwell's equations.

We show that shape gradients of PDE constrained shape functionals can be stated in two equivalent ways. Both rely on solutions of state and adjoint boundary value problems (BVPs). We proved that volume based expressions enjoy faster convergence rates than boundary integrals in a finite element setting.

Speaker's biography

Since June 2011, I have been a PhD candidate in Institute of Electromagnetic Fields, ETH Zurich, Switzerland. I received the B.Sc. and M. Sc. degrees in Electrical Engineering both from University of Tehran, in 2006 and 2009, respectively.

I am broadly interested in theoretical and experimental aspects of optics, plasmonics, THz, and radio frequency, as well as shape calculus and optimization. In my research, I use numerical methods such as Finite Elements and Finite Differences to simulate and optimize several optical and plasmonic nano-particles.