Collaborative Knowledge Construction using an Online Annotation System, at 2016 International Conference of East-Asian Association for Science Education (Tokyo, Japan), Friday, August 26, 2016
We studied the collaborative construction of knowledge facilitated by an online annotation system in a flipped class. Students used the online system to collaboratively annotate the pre-class reading assignments by asking questions, responding to questions, or placing comments. The annotation threads reveal the students’ knowledge structures. For example, asking questions (or answering them) exposes lack of knowledge or misconceptions that persist after the pre-class reading. At the same time, even just reading annotation threads without contributing to them can help spread knowledge.... Read more about Collaborative Knowledge Construction using an Online Annotation System
Nonlinear Phase-Matching in 2D Integrated Zero-Index Metamaterials, at MRS: Optical Metamaterials - From New Plasmonic Materials to Metasurface Devices (Boston, MA), Wednesday, December 2, 2015:
Nonlinear optics play an important role in many applications in photonics and quantum optics, such as in frequency conversion, sensing, and entangled-photon generation. The strong field confinement obtained by the transition to an integrated platform has led to unprecedented nonlinear figures of merit and the miniaturization of nonlinear devices. However, phase-matching remains an essential component to nonlinear processes and represents a significant obstacle, with many different free-space and on-chip techniques being developed to circumvent its constraints. Recently, a 1-dimensional... Read more about Nonlinear Phase-Matching in 2D Integrated Zero-Index Metamaterials
Zero-index waveguides for metasurface applications, at 2015 MRS Fall Meeting (Boston, Massachusetts), Wednesday, December 2, 2015:
Metamaterials with a refractive index of zero have emerged as a new tool for phase control in nanophotonics. Waves propagate within such metamaterials with infinite phase velocity, resulting in uniform phase throughout. Recently two-dimensional zero-index metamaterials have been integrated with on-chip silicon photonics, allowing for phase-free propagation over large areas. However, zero-index modes are inherently lossy: since the momentum of the wave is zero, it lies above the light line, and therefore couples to waves in free space. In particular, momentum conservation implies that the... Read more about Zero-index waveguides for metasurface applications
Direct Laser Writing of 3D Gratings and Diffraction Optics, at CLEO: Science and Innovations Laser-Induced Structuring in Bulk Material (SW1K) (San Jose, CA), Wednesday, May 13, 2015:
We fabricate 3D gratings and diffraction optics using direct laser writing. Diffraction patterns of gratings agree with Laue theory. We demonstrate zone plates for visible wavelengths. Direct laser writing is promising for integrated diffraction optics.
Plasmonic Cell Transfection using Micropyramid Arrays, at SPIE Photonics West, SPIE (San Francisco, CA), Sunday, February 8, 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 introduce an emerald green fluorescent protein (EmGFP) reporter plasmid into the cells to determine the LSP-mediated transfection... Read more about Plasmonic Cell Transfection using Micropyramid Arrays
Exclusively-visual analysis of classroom group interactions, at American Association of Physics Teachers Winter Conference (San Diego, CA), Sunday, January 4, 2015:
Data that measures group learning are time-consuming to collect and analyze on a large scale. As an initial step towards scaling qualitative classroom observation, our team qualitatively coded classroom video using an established coding scheme with and without its audio. We find that inter-rater reliability is as high when using visual data only—without audio—as when using both visual and audio data to code. Also, inter-rater reliability is high even when comparing use of visual and audio data to visual-only data. We see a small bias that interactions are more often coded as group... Read more about Exclusively-visual analysis of classroom group interactions
Dirac-cone based negative/zero/positive refractive index metamaterials, at SPIE Photonics West: Photonic and Phononic Properties of Engineered Nanostructures IV (San Francisco, California), Thursday, February 6, 2014
Based on accidental degeneracy, a Dirac-cone can be formed at the center of the Brillouin zone of a photonic crystal, which can be treated as a homogeneous bulk metamaterial in the vicinity of Dirac-point. In the vicinity below (above) the Dirac-point, the backward-wave (forward-wave) implies negative (positive) n_eff; at Dirac-point, k=0 induces zero n_eff. This negative/zero/positive refractive index shows low-loss and good impedance matching to free-space. According to this principle, we designed a Dirac-cone based metamaterial consisting of 2D square array of silicon pillars operating... Read more about Dirac-cone based negative/zero/positive refractive index metamaterials