Alexander Tait
NIST: National Institute of Standards and Technology

Abstract

At low-temperature, silicon can be made to emit light, and superconducting wires can detect single photons. When integrated with silicon photonic waveguides, this combination of sources and detectors forms the basis of an emerging platform for cryogenic silicon photonics. A new photonic integrated circuit platform could potentially impact current approaches to quantum measurement, communication, and computing. The extent of these potentials depends on further development of on-chip silicon light sources. There are two frontiers: high-power sources for nonlinear optics, and very low-power (single-photon) sources for quantum optics.

Silicon photonics has opened possibilities for new concepts in optical information science - this is also true at room temperature. Neuromorphic silicon photonics has pushed the bounds of machine learning performance. As with any revolutionary computing technology, neuromorphic photonics could have unforeseen and fascinating other applications, perhaps most dramatically in autonomous analysis and control of ultrafast phenomena.

This talk will summarize recent progress in neuromorphic silicon photonics and touch on some current research frontiers. I will give an introduction to cryogenic silicon optoelectronics and describe how these physics can connect to information processing. Special attention will be given to current progress and future directions in cryogenic all-silicon light sources.

 

Ziqing Hong
Northwestern University

Abstract

Dark matter is a hypothetical form of matter that, if it exists, may account for more than a quarter of the energy density of our universe. Despite the variety of astrophysical evidence pointing to its existence, the direct interaction of dark matter in a terrestrial detector is yet to be observed. The Super Cryogenic Dark Matter Search (SuperCDMS) experiment tries to observe a dark matter signal in silicon and germanium detectors operated around 50 miliKelvin. In this talk, I will discuss the status of the next generation SuperCDMS experiment, the recent results with an eV-resolution gram-scale prototype detector, and the future plan with this technology.

 

Dr. Shawn Westerdale
Princeton University

Abstract

Dark matter comprises 27% of the energy density of the universe -- about 5 times more than baryonic matter. Despite this abundance, its nature remains a complete mystery. While several theories predict different dark matter candidates, no experimental evidence to date can confirm any of them. Many experimental efforts are currently underway, aiming to directly detect some of the most promising candidates — a challenge akin to finding a needle in a haystack. To accomplish this, large detectors can be built deep underground, where backgrounds are greatly reduced. In this colloquium, I will review techniques used to search for dark matter, focusing on the DarkSide-50 and DEAP-3600 liquid argon-based detectors. I will discuss significant advances that have been made in reducing backgrounds for these dark matter searches and in improving liquid argon detector technology, paving the way for a future set of detectors to probe low- and high-mass candidates. 

Dr. Westerdale is a candidate for the tenure-track faculty position in Particle Astrophysics.  Faculty are encouraged to meet with Dr. Westerdale during his 2 days of visits.  Students and postdocs are welcome to join for a catered lunch immediately following the colloquium in Stirling 201.

 

Dr. Laurie Barge
Research Scientist in Astrobiology at the NASA Jet Propulsion Laboratory

Abstract

To search for biology on other worlds, it is important to have working definitions of what constitutes “life” and “non-life”. However, the distinction between biotic and abiotic is often unclear, since we are still learning about the limits of life, and also because abiotic systems can become highly complex when devoid of biological influence. Although Earth provides a variety of examples of what biology can look like, examples of the critical steps between abiotic and biotic systems are lacking because the prevalence of life on our planet has contaminated / erased its record of prebiotic conditions. However, prebiotic chemistry may still be a current or formerly active process on other worlds with detected chemical gradients and organics, such as Enceladus, Ceres, or Mars. I will discuss how astrobiologists approach the search for life on other planets, and will describe some of the difficulties in distinguishing living and non-living systems. In particular I will share some of our lab work on simulating gradients in hydrothermal vents that could support life or its origin, and prebiotic chemistry experiments that aim to bridge the gap between geochemistry and the emergence of biochemistry.

Bio

Dr. Laurie Barge is a Research Scientist in Astrobiology at the NASA Jet Propulsion Laboratory. She co-leads the JPL Origins and Habitability Laboratory which studies the origin of life and how life can be detected on other planets, and she is the Investigation Scientist for the HiRISE instrument on NASA’s Mars Reconnaissance Orbiter (MRO). Dr. Barge’s research interests include the emergence of life on Earth, and organic chemistry on Mars and ocean worlds such as Jupiter’s moon Europa and Saturn’s moon Enceladus. She is also interested in hydrothermal vents as planetary analogs, and is the science lead for an underwater laser divebot that will be deployed to a vent in the Pacific in 2020. Dr. Barge received her Bachelor’s degree (2004) in Astronomy and Astrophysics from Villanova University, and her Ph.D. (2009) in Geological Sciences from the University of Southern California. After graduate school she was a Caltech postdoc and then NASA Astrobiology Institute postdoctoral fellow. For her astrobiology research Barge has received the JPL Lew Allen Award, the NASA Early Career Public Achievement Medal, and the Presidential Early Career Award for Scientists and Engineers.

 

Szymon Manecki
SNOLAB

Abstract

Our World is a wealthy mine of fundamental properties waiting to be explored. Two of the most intriguing mysteries are the dominance of matter over anti-matter, as well as the nature of dark matter in the Universe. Canada, with SNOLAB and its partners are at the forefront of making these discoveries in the upcoming decades. The SNO+ experiment is soon going to begin the search for neutrinoless double beta decay, known as one of the most promising probes to study the matter asymmetry in the Universe. ARGO on the other hand, is a concept for a future large-scale liquid-argon detector. In exploring the unknown nature of dark matter, ARGO will search for its possible direct interactions with ordinary matter with unprecedented sensitivity.

In this colloquium, I will present the status, development and prospects for these two projects. I will also highlight their competitiveness and complementarity in the field.

 

Orad Reshef
University of Ottawa, Ontario

Abstract

The refractive index is the single defining quantity for determining the behaviour of light propagation in a medium. Recent advances by the metamaterials community have resulted in fine control over this value in both composite and bulk materials, tuning the index to negative values and even down to zero [1]. These exotic materials exhibit extreme and counter-intuitive properties, including infinite phase velocities and seemingly diverging optical nonlinearities.

In my talk, I will first discuss the recent progress in developing monolithic zero-index metamaterials in the standard silicon-on-insulator platform [2], and how we used this material to produce and directly image light waves with infinite wavelengths at optical frequencies [3]. I will then present our recent experiments exploiting the giant ultrafast nonlinearities of another low-index material, indium tin oxide, and how this class of materials enters a non-perturbative regime of nonlinear optics [4]. Our work has important implications for the fundamental understanding of nonlinear optical phenomena and enables novel applications in ultra-thin active photonics devices.

Bio

Dr. Orad Reshef is working in nanophotonics, metamaterials and nonlinear optics. After completing a bachelor’s degree with First Class Honours in Physics at McGill University in Montreal, he joined Prof. Eric Mazur at Harvard University to pursue his doctoral studies. There, he worked on photonic titanium dioxide, integrated zero-index metamaterials, and their applications in nonlinear optics. Currently, Orad is a Banting postdoctoral fellow under Robert Boyd in the CERC group at the University of Ottawa, where he is working on nonlinear optics in epsilon-near-zero (ENZ) materials, high-Q metasurfaces based on surface lattice resonances, and nonlocal metamaterials. He is interested in scalable integrated photonic devices, and on engineering nonlinear interactions and devices that are not typically found in nature by structuring materials on the nanoscale. More information on Orad can be found online on his portfolio website: reshef.ca

Laurence Perreault Levasseur
University of Montreal

Abstract

Despite the remarkable success of the standard model of cosmology, the inflationary lambda CDM (cold dark matter) model, at predicting the observed structure of the universe over many scales, very little is known about the fundamental nature of its principal constituents: the inflationary field(s), dark matter, and dark energy. In this talk, I will give a brief overview of the successes of the inflationary lambda CDM model and discuss how, in the coming years, new surveys and telescopes will provide an opportunity to probe these unknown components. These surveys will produce unprecedented volumes of data, the analysis of which can shed light on the equation of state of dark energy, the particle nature of dark matter, and the nature of the inflation field. The analysis of this data using traditional methods, however, is entirely impractical. I will share my recent works in developing machine learning tools for cosmological data analysis and discuss how they can allow us to overcome some of the most important computational challenges for the data analysis of the next generation of sky surveys.

Mark Wilson
University of Toronto

Abstract

The ability to efficiently convert low-intensity light between the visible and infrared would be an enabling technology—particularly for applications such as 3rd-generation photovoltaics, biological imaging, and sensitized silicon focal plane array detectors with cost-effective response in the short-wave infrared (SWIR; λ:1‒3µm). Accordingly, we are advancing our new approach that combines two excitonic materials—conjugated organic molecules and colloidal quantum dots—to achieve broadband, non-coherent photon up-conversion from the SWIR to the visible. 

To achieve upconversion, we synthesize lead sulfide nanocrystals that can absorb infrared photons, and fabricate devices where these excitations sensitize the spin-triplet excited state of a nearby organic semiconductor (e.g. rubrene). In the molecules, strong exchange-splitting allows the excitonic energy to be combined via triplet fusion to create visible light. To-date, in solid state devices, we have observed upconversion from light at the threshold of the SWIR (λ=1.1μm→612nm),1 and have achieved upconversion efficiencies of 7±1% with λ=808 nm excitation by using ligand engineering to optimize Dexter-mediated nanocrystal→molecule energy transfer.2

However, although colloidal quantum dots are attractive SWIR sensitizers— their optical gap can be tuned during synthesis, and their photoexcitations are functionally spin-mixed at room temperature—there is much more to be done. For instance, while transient spectroscopy shows that our SWIR upconversion approach could be maximally efficient with only 1/10th the intensity of natural sunlight1, poor exciton transport in the nanocrystal films—due in part to energetic disorder resulting from size-dispersity and quantum confinement—presently hinders light gathering and hampers low-intensity performance. Here, our recent work has uncovered that a pre-nucleation cluster intermediate has historically frustrated efforts to synthesis low-dispersity ensembles of small (⌀<4 nm) PbS nanocrystals, and showed that process additives can enable one-step growth and yield markedly narrower heterogeneous linewidths.3 Further, our recent experiments with a novel molecular dimer in solution suggest that asymmetric coupling between triplet-pair spin states can allow the overall-quintet state to play a beneficial role in the kinetic scheme of triplet fusion, ultimately lifting the expected spin-statistical efficiency limit from 25% to 66%,4 and offering a route to all-in-one free-floating upconverting fluorophores for imaging.

References

1. Wu, M.; Congreve, D. N.; Wilson, M. W. B.; Jean, J.; Geva, N.; Welborn, M.; Van Voorhis, T.; Bulović, V.; Bawendi, M. G.; Baldo, M. A. Solid-State Infrared-to-Visible Upconversion Sensitized by Colloidal Nanocrystals. Nature Photonics 2016, 10 (1), 31–34.
    
2. Nienhaus, L.; Wu, M.; Geva, N.; Shepherd, J. J.; Wilson, M. W. B.; Bulović, V.; Van Voorhis, T.; Baldo, M. A.; Bawendi, M. G. Speed Limit for Triplet-Exciton Transfer in Solid-State PbS Nanocrystal-Sensitized Photon Upconversion. ACS Nano 2017, 11 (8), 7848–7857.
    
3. Green, P. B.; Narayanan, P.; Li, Z.; Sohn, P.; Imperiale, C. J.; Wilson, M. W. B. Controlling Intermediates in the Synthesis of PbS Nanocrystals. Submitted 2020.
    
4. Imperiale, C. J.; Green, P. B.; Miller, E. G.; Damrauer, N. H.; Wilson, M. W. B. Triplet-Fusion Upconversion Using a Rigid Tetracene Homodimer. The Journal of Physical Chemistry Letters 2019, 7463–7469.

Tami Pereg-Barnea
McGill University

Abstract

The interest in topological condensed matter dates back to the early days of the quantum Hall effect in the late 80's. Back then though, the role of topology was not entirely clear and it was thought that the interesting physics of the quantum Hall effect are unique to systems where time reversal invariance is broken. The excitement therefore grew with the discover of time-reversal invariant topological insulators in 2005.  This has led to the Nobel prize of 2016, awarded to some of the field's pioneers - Kosterlitz, Thouless and Haldane.

The introduction of topology to the classification of states of matter is arguably one of the most important paradigm shifts of our time. We now understand that states of matter should be classified not only by their dimensionality and symmetries (the notions in heard to Landau's Fermi liquid theory) but also by their topological properties.

In this talk I will present a biased view of the advances in the field and the challenges ahead. I will organize the discussion in three parts: fundamental, complex and applications. The 'fundamental' part will include research done in the direction of organizing the possible phases of materials and some known examples. The 'complex' part will focus on research into topological condensed matter systems beyond the clean, equilibrium and non-interacting limits and the 'applications' part will discuss driving, manipulating and realizing topological systems and possible applications.

Matt Dobbs
McGill University Physics and CIfAR Senior Fellow

Abstract

Technology advances have opened a new era of radio observations. We are now monitoring the sky at millisecond cadence and discovering a vast catalog of new fast radio transients while simultaneously making deep maps of structure in the universe using hydrogen intensity mapping as a tracer. While these fields are still in their infancy, early results are rolling out, fuelling discovery and motivating the design for new instruments.