Ignacio Franc
University of Rochester

 

Abstract

Ultrashort light pulses play a critical role in our quest to observe and exploit ever-faster physical phenomena. In particular, few-cycle lasers with frequencies in the visible range enable the visualization and control of chemical and physical processes occurring on femto to attosecond timescales. In this talk, I will discuss how the interaction of these intense and ultrafast light fields with matter can be used to guide electrons in matter and to modify the electronic properties of materials on demand. Specifically, I will discuss how it is now possible to use few cycle pulses to generate ultrafast laser-induced currents and design logical circuits elements that operate 106 times faster than present-day capabilities. Further, I will introduce a method that now enables modeling and interpreting the effective response properties of laser-dressed materials. Remarkably, in these highly non-equilibrium systems the Floquet states emerge as the natural states to characterize their physical properties. Using it, we isolate purely-optical tell-tale signatures of the emergence of Floquet states that can be used to investigate their formation and survival under experimentally relevant conditions.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Rayf Shiell
Trent University

 

Abstract

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Stéphane Kéna-Cohen
Polytechnique Montreal

 

Abstract

In this talk, we will discuss two recent observations from our group that have challenged widespread assumptions held (by us included!) about the optical response of commonly used optical materials: that material polarization can safely be considered to respond locally to the electric field and that the second-order nonlinear response of amorphous films should vanish due to centrosymmetry. In the first part of the talk, we will describe our proposal for a new type of optical antenna dubbed a "photonic gap antenna", and our realization of its extreme version where an epsilon-near-zero (ENZ) material is enclosed within the gap. Such antennas can provide electric field enhancements of >100 and large Purcell factors without requiring stringent nanofabrication. To our surprise, when measurement third harmonic generation as a proxy for field enhancement, sharp peaks emerge in the response that are completely absent in our full wave electromagnetic calculations. We find that the appearance of these peaks can only be explained when including nonlocality in the dielectric response of the ENZ material. Nonlocal simulations show that the volume averaged field enhancement can be 4–6 greater than that predicted by the local model, which becomes an important consideration when designing optical devices. In the second part of the talk, we will describe our recent discovery that amorphous thermally evaporated organic thin films of small molecules can have second-order optical nonlinearities on par with those of state-of-the-art nonlinear materials (c(2)31, c(2)33 >50 pm/V), with the important advantage that they can be deposited on arbitrary photonic platforms. We will show that by harnessing the interplay between the permanent dipole moment and surface energy minimization, it is possible to spontaneously break centrosymmetry during thermal evaporation, without the need for special alignment procedures. In addition to its applications in photonics, this observation has allowed us to better understand molecular alignment beyond the mean molecular orientation angle.

 

Biosketch

Stéphane Kéna-Cohen is a Full Professor of Engineering Physics at Polytechnique Montréal, where he heads the Light-Matter Group and is the Canada Research Chair in Light-Matter Photonics. His group works both on the development of advanced optoelectronic components and in better understanding and harnessing light-matter interaction in novel materials. His group is widely recognized for pioneering advances in understanding and exploiting the strong light-matter coupling regime in optical microcavities at room-temperature. Other recent achievements include the development of record efficiency near infrared organic light-emitting diodes, the first 2D material-based mid-infrared light-emitting diodes, the observation of superfluidity of light and the realization of photonic XY Hamiltonian lattices using polariton condensates. He obtained his PhD in 2010 as a Gordon Wu scholar at Princeton University under the supervision of Stephen R. Forrest and was a Junior Research Fellow at Imperial College London, working closely with Stefan A. Maier and Donal D.C. Bradley before joining Polytechnique Montréal.

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

Mark Chen
Queen's University

 

Abstract

In this colloquium, I’ll talk about liquid scintillator neutrino detectors. SNO+ is the Sudbury Neutrino Observatory (SNO) filled with liquid scintillator. I’ll present recent (preliminary) results from SNO+ including measurements of the oscillation of neutrinos from nuclear power reactors in Ontario and the detection of geoneutrinos. I’ll also describe the upcoming 3rd phase of SNO+ that will dissolve tellurium in the liquid scintillator to search for neutrinoless double beta decay, seeking to understand the origin of neutrino mass and their matter-antimatter properties. If time permits, I’ll also talk about some of my recent research on “opaque” liquid scintillators.

Timbits, coffee, tea will be served in STI A before the colloquium.