Research from the Departments of Chemistry at Simon Fraser University (SFU) and the University of Washington (UW) has uncovered an overlooked physical process that allows optical energy to move more efficiently within a nanosystem. The research could pave the way for of the invention of new devices for optical sensing, optical communications and more.
SFU Chemistry professor and associate chair Byron Gates leads the Gates Research Group, and is a cofounder and primary user of SFU’s 4D LABS, one of the university’s core facilities. Gates' work focuses on enhancing properties of nanomaterials used to create technologies for use in optical sensing, biological imaging, drug delivery, fuel cells and batteries.
He has been leading research in collaboration with UW to develop and test a new strategy to improve nonlinear optical processes at the nanoscale. These processes convert incoming light of a single color to outgoing light of one or more different colors that is “trapped” and ready for use within microchip-sized devices. However, while nonlinear optics has been studied for decades, conversion of light from one color to another is extremely inefficient at smaller scales, limiting the usefulness of any practical devices. The SFU/UW team’s work unlocks a new set of design ideas to help future scientists and engineers overcome this limitation in downstream technologies.
The research was carried out by graduate students Rana Faryad Ali (SFU), and Jacob A. Busche (UW), both of whom have since graduated with PhDs, along with Saeid Kamal from the Laboratory for Advanced Spectroscopy and Imaging Research (LASIR), professor David J. Masiello (UW) and Gates. Under the guidance of the team’s senior members, Ali and Busche developed experiments and theories that ultimately led to the team’s exciting results.
The article Near-field enhancement of optical second harmonic generation in hybrid gold–lithium niobate nanostructures explains the discovery in detail. It was published this week in Light: Science & Applications.
The research team who worked on this discovery [l-r]: Rana Faryad Ali (SFU), Jacob Busche (UW), Saeid Kamal (LASIR), David Masiello (UW), Byron Gates (SFU).
We spoke with researchers Gates, Ali and Busche about their work.
Tell us about the problem or challenge you identified and how your research has the potential to overcome it.
Ali, Busche, and Gates: Current designs for devices that efficiently confine, transform and transfer light at the nanoscale are limited by their need for carefully arranged nanoscopic parts made of different materials. Our research highlights that there are more ways than previously thought to arrange and design these parts without sacrificing efficiency gains. The results presented in our manuscript will help expand the variety of viable nonlinear optical device designs while also reducing the need for such precise nanoengineering.
This research was conducted over several years. Can you tell us about the research process? Was there an “aha!” moment?
Busche: I started theory work in 2020 and spent several months chasing a simple but ultimately incorrect hypothesis based on data provided by Byron, Faryad and Saeid. Then I hunted down a second idea that turned out to only show that certain effects could not be contributing to the signal. It was my third idea that bore fruit, namely a model that provides a physical explanation for the observed signals alongside quantitative reproduction of the experimental data. So, no “aha!” moment for me, but more of a slow and steady approach to a conclusion.
Ali: I was fortunate to work under the supervision of professor Gates during my PhD, where I learned about creativity and innovation in science. Byron is a pioneer in nanoscience, and encouraged me to pursue this project, provided critical feedback to improve the science behind the project and enabled me to access all the resources required for the research.
The Gates Lab is like a "playground" for students, who can choose from several different research areas. Byron has an interest in many areas of science. We have had a number of "aha" moments in our research. For example, controlling the number of gold nanoparticles on the lithium niobate was a challenge, but we did achieve that goal thanks to Byron’s guidance. Similarly, our awesome collaborators from UW developed a brand-new theoretical model to prove our experimental results where we said "aha" many times.
Gates: It is important to recognize that expertise is not born overnight. Just as an Olympic athlete spends years advancing and honing their skills, we have the same opportunity provided to us through our academic training. It requires a careful set of hypotheses, a long-term commitment, a willingness to receive critical feedback and to strive to learn from this and, as demonstrated through this project, a breadth of expertise on the team.
I thoroughly enjoy working on collaborative projects like this where you can not only bring your own experiences and expertise to the table, but also work with others at the forefront of their field. This project required a long-term dedication of all team members to strive for understanding over the pressure to publish something quickly and incomplete. I can proudly say that Faryad and Jake demonstrated a commitment to the project and to advancing their own expertise akin to the training of an Olympian. There is a satisfaction in finding and validating one’s scientific hypothesis through multiple trials and through a series of distinct analyses.
What are some of the applications for this recent discovery? Where will you go next with this line of inquiry?
Busche: It is too early to tell, however there are several possible application routes we can already see, mostly regarding very small imaging and sensing devices where nonlinear effects are used to artificially extend the functional wavelength range of an existing detector. We provide references for some of these applications in the paper, however our real scientific goal was to uncover the operative physical mechanisms behind the surprising experimental signals and translate our findings into a broad set of new device design ideas rather than to invent a specific application or set of applications.
My current work is focused on the ways that nonlinear optical nanostructures emit light with quantum properties. Perhaps, in the future, my quantum work and our nonlinear enhancement work will dovetail to provide new insights for the design of practical devices in sensing, imaging, switching or waveguiding that operate at very small scales where quantum effects are important and useful.
Ali: Our work could lead to several applications, for example: high-speed optical communications such as quantum optics; optical sensing; imaging biological samples, such as cells and tissues with high spatial resolution and contrast; and photovoltaics, the enhanced conversion of light into energy from solar cells.
Gates: There are many options as Jake and Faryad have outlined, but we really don’t know yet where the highest impact will be. In the near term, the knowledge resulting from our studies will most likely be used in advancing the design of other optical materials.
For example, techniques that employ optical nanostructures such as antennas, superlenses and/or contrast agents have been studied for many years as they are crucial for the development of next generation light harvesting and detection devices. However, the design and demonstration of new nanostructured optical materials alongside developing a detailed understanding of the phenomena behind their performance will enable novel nonlinear optical materials and methods.
This understanding will also enable the development of more effective and more widely adopted materials and methods. I anticipate that there will also be further fundamental knowledge learned that builds upon our studies with respect to the interactions of nanomaterials and light, and the phenomena behind these interactions on a single-particle level.
Several labs and locations undertook this research. How important was collaboration in the success of this work?
Busche: Collaboration between experiment and theory was the single most crucial piece of this investigation. There were several rounds of experiments done to meet the needs of the theory team as we slowly proved our initial hypotheses wrong. We regularly held multi-team discussions to build and refine new questions, and Faryad and I spent a very large number of hours together on Zoom funneling our ideas, data and results into the manuscript. All in all, working with the SFU group has been an ideal experience that has highlighted the value of bringing many minds and skillsets together to solve large, difficult problems.
Ali: Jake and professor Masiello demonstrated their true passion for science with an understanding that through new knowledge comes new opportunities. They were persistent in this collaborative effort to accomplish our goal of moving the field forward through a series of thoughtfully and carefully designed investigations.
Gates: It is not the location of the work that matters. It is the nature of the people involved in the project. This project was the result of the persistence of both Faryad and Jake, and the patient support, knowledge and guidance of all members of the team. The outcome reflects all of the team members and their dedication to seeking understanding through a set of carefully designed and tested hypotheses.
Do you have any advice or insights for students who are interested in pursuing research in nanoscience at SFU?
Ali: The Gates Group is a dynamic lab in the field of nanotechnology, pushing the boundaries of scientific exploration in Canada. The research themes in the Gates group are focused on understanding the fundamental properties of materials and harnessing the incredible potential of nanostructures across a wide range of disciplines, from catalysis and energy storage to photonics and biomedical sciences. For me, it was great because I have had a diverse training experience and now I can explore interdisciplinary questions and lead the projects wherever I want without limitations. Byron will give people a chance that other people won't necessarily be willing to offer. A lot of people, including me, whom Byron has given a chance, have really thrived. I am aspiring to become a professor and will adopt his research philosophy in my team, too.
Rana Faryad Ali using the analytical transmission electron microscope at SFU's 4D LABS, a state-of-the-art facility that makes the development and study of nanomaterials possible.
To learn more about the work to advance nanoscience visit: Gates Research Group.
This work was supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the British Columbia Knowledge Development Fund, Western Economic Diversification Canada and the U.S. National Science Foundation.
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