“Trapped Rainbow” Effect within Graded Gratings for Localization and Detection of THz Frequency Components

Arthur Montazeri

Kherani Group, Photonics

Abstract:

Plasmonic gratings are shown to confine electromagnetic radiation at specific locations within the structure. These ultra-wideband structures are thus able to spatially resolve various frequencies of a broadband source. Each resolved frequency component is then temporally trapped within the grating. This is because the dispersion relation of the SPPs depends on the dimensions of the grating. As a result, the group velocity decreases as the grating depth increases and the frequency components come to a standstill at different spatial positions. In the visible light region of the electromagnetic spectrum, this gives rise to a rainbow-like effect over the structure. Extending this to the IR regime, where ``rainbow trapping'' no longer refers to the visible light, we find a parallel phenomenon.

It has been also shown both theoretically and experimentally, that strong fields of surface plasmon polaritons at visible frequencies can be efficiently coupled to nano-structures placed in close proximity. I will talk about the integration of graded gratings and tunnelling nano-diodes, to attain a tunable detector at THz frequencies corresponding to the IR range. In this setup, nano-antennas connected to metal-insulator-metal (MIM) diodes are placed within the grating to detect the radiation through rectifying the high frequency signal. These nano-antennas are optimized for the particular frequency of interest at these locations.

Biography:

Arthur is a graduate of Engineering Physics from McMaster University. As an undergrad and a year thereafter, he worked as a research assistant in the physics department studying the problem of anomalous diffusion of large molecules in the crowded cellular environment.

He subsequently worked in the industry for four years, returning eventually to McMaster to for a Master’s degree in electrical engineering. His thesis was on developing absorbing boundary conditions for FDTD simulations of electro-acoustic waves. These waves, which surface acoustic waves are an example of, are coupled mechanical and acoustic waves. As a result, in every propagation direction, there are in general ten coupled solutions, making the numerical equations quite a mess. 

Commencing a PhD program in 2011, he moved on to plasmonics electromagnetic waves, where he has been working on structures where light couples to electrons resulting in slowing down and trapping of electromagnetic waves.