Nonequilibrium materials: using ultrafast laser pulses to change band structures, at SPIE Conference on Ultrafast Bandgap Photonics (Baltimore, MD), Sunday, April 17, 2016:
Soon after it was discovered that intense laser pulses of nanosecond duration from a ruby laser could anneal the lattice of silicon, it was established that this so-called pulsed laser annealing is a thermal process. The past two decades have show that ultrashort laser pulses in the femtosecond regime can induce athermal, nonequilibrium processes that lead to either transient phase changes in semiconductors through ultrafast ionization or permanent phase changes through nonequilibrium doping. In this talk we will review work in both of these regimes and show how ultrafast lasers can be used... Read more about Nonequilibrium materials: using ultrafast laser pulses to change band structures
Less is More: Extreme Optics with Zero Refractive Index, at Photonics West 2016, Integrated Optics: Devices, Materials, and Technologies XX (San Francisco, CA), Monday, February 15, 2016:
Nanotechnology has enabled the development of nanostructured composite materials (metamaterials) with exotic optical properties not found in nature. In the most extreme case, we can create materials which support light waves that propagate with infinite phase velocity, corresponding to a refractive index of zero. This zero index can only be achieved by simultaneously controlling the electric and magnetic resonances of the nanostructure. We present an in-plane metamaterial design consisting of silicon pillar arrays, embedded within a polymer matrix and sandwiched between gold layers. Using an... Read more about Less is More: Extreme Optics with Zero Refractive Index
On-chip zero index metamaterials, at Advanced Laser Applications Workshop, Korea Institue of Machinery and Materials (Daejeon, South Korea), Friday, August 28, 2015:
Impedance-matched metamaterials with zero refractive index can be achieved by exploiting a Dirac cone at the center of the Brillouin zone. We present an in-plane Dirac-cone metamaterial consisting of low-aspect-ratio silicon pillar arrays in an SU-8 matrix with top and bottom gold layers. Using an integrated nano-scale prism constructed of the proposed material, we demonstrate unambiguously a zero refractive index in the optical regime. This design serves as a novel on-chip platform in the optical regime to explore the exotic physics of Dirac-cone metamaterials and to implement applications... Read more about On-chip zero index metamaterials
Stopping time, at International Year of Light Special Lecture at the 11th Conference on Lasers and Electro- Optics Pacific Rim (CLEO-PR 2015) (Busan, South Korea), Monday, August 24, 2015:
Time is of philosophical interest as well as the subject of mathematical and scientific research. Even though it is a concept familiar to most, the passage of time remains one of the greatest enigmas of the universe. The philosopher Augustine once said: "What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know." The concept time indeed cannot be explained in simple terms. Emotions, life, and death - all are related to our interpretation of the irreversible flow of time. After a discussion of the concept of time, we will review... Read more about Stopping time
Teaching Physics, Conservation Laws First, at Siam Physics Congress 2015 (Krabi, Thailand), Thursday, May 21, 2015:
The Principles and Practice of Physics is a groundbreaking new calculus-based introductory physics textbook that uses a unique organization and pedagogy to allow students to develop a true conceptual understanding of physics alongside the quantitative skills needed in the course. The book organizes introductory physics around the conservation principles and provides a unified contemporary view of introductory physics. In this talk we will discuss the unique architecture of the book, the conservation-laws-first approach, and results obtained with this book.
Assessment: The silent killer of learning, at Siam Physics Congress 2015 (Krabi, Thailand), Wednesday, May 20, 2015:
Why is it that stellar students sometimes fail in the workplace while dropouts succeed? One reason is that most, if not all, of our current assessment practices are inauthentic. Just as the lecture focuses on the delivery of information to students, so does assessment often focus on having students regurgitate that same information back to the instructor. Consequently, assessment fails to focus on the skills that are relevant in life in the 21st century. Assessment has been called the "hidden curriculum" as it is an important driver of students' study habits. Unless we rethink our approach to... Read more about Assessment: The silent killer of learning
High Throughput Poration of Mammalian Cells using Femtosecond Laser-activated Plasmonic Substrates, at Tokyo Metropolitan University (Tokyo, Japan), Thursday, January 29, 2015:
We present a new cell transfection method that uses femtosecond laser-excited localized surface plasmons (LSPs) on a nanostructured micropyramid array. Our gold-layered micropyramids have nano-apertures at the apex to form high local electric field enhancements, or “hot spots.” These hot spots form microbubbles that temporarily perforate mammalian cell (HeLa S3) membranes and allow dye molecules and plasmid vectors to diffuse through the membrane openings. We optimize our laser parameters for successful poration and high cell viability. Our nontoxic, efficient, and scalable technique... Read more about High Throughput Poration of Mammalian Cells using Femtosecond Laser-activated Plasmonic Substrates
Flat space, deep learning, at GIREP-MPTL International Conference on Teaching/Learning Physics: Integrating Research into Practice, University of Palermo (Palermo, Italy), Tuesday, July 8, 2014:
The teaching of physics to engineering students has remained stagnant for close to a century. In this novel team-based, project-based approach, we break the mold by giving students ownership of their learning. This new course has no standard lectures or exams, yet students’ conceptual gains are significantly greater than those obtained in traditional courses. The course blends six best practices to deliver a learning experience that helps students develop important skills, including communication, estimation, problem solving, and team skills, in addition to a solid conceptual understanding... Read more about Flat space, deep learning
Black silicon and the quest for intermediate band semiconductors, at Laser-Based Micro and Nano Processing VIII, Photonics West 2014 (San Francisco, CA), Thursday, February 6, 2014:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Black silicon and the quest for intermediate band semiconductors