Phase-Matching in Dirac-Cone-Based Zero-Index Metamaterials, at CLEO: Science and Innovations (San Jose, CA), Sunday, June 5, 2016:
Using nonlinear scattering theory, we simulate nonlinear signal generation in 2-dimensional zero-index metamaterials based on a photonic Dirac cone at the G point. We observe unique phase-matching in multiple simultaneous directions as the index approaches zero.
Inverse Transformation Optics with Realistic Material Parameters, at META'15 (New York, New York), Thursday, June 4, 2015:
We present a method to generate transformation functions based on a space of achievable material properties. To validate this approach, we consider the range of effective refractive index achievable using silver nanowires in a dielectric background. Given fabrication constraints, we generate a reduced cloaking transformation and confirm its performance using FDTD and FEM simulations. We explore conditions for finding appropriate mappings in restricted parameter spaces, and strategies for optimizing transformations to account for absorption and scattering.
Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics, at MRS 2014 Fall Meeting and Exhibit, Symposium L: Optical Metamaterials and Novel Optical Phenomena Based on Nanofabricated Structures (Boston, MA), Thursday, December 4, 2014
Integrated diffractive optics has many applications in beam shaping and control on the micro-scale. Fabrication using lithography is limited to planar or layered geometries. We demonstrate fabrication of diffractive elements via direct laser writing. We have tested 3D diffraction gratings and zone plates designed for operation at visible wavelengths. Direct laser writing is a promising technique to fabricate integrated 3D and multi-layer diffraction optics. We have previously developed a laser writing technique that enables fabrication of disconnected metal structures in a polymer matrix,... Read more about Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics
Subcellular surgery and nanosurgery, at Photonics West 2014 (CA), Thursday, February 6, 2014:
Gene therapy is the use of DNA as an agent to cure or slow down the progression of a disease. A crucial requirement for gene therapy is the efficient and safe introduction of genetic vectors into mammalian cells. We developed a high-efficiency, low-toxicity, spatially-selective and high-throughput transfection method using fs laser induced-plasmons on a nanostructured substrate. We specifically compare two designs of plasmonic substrates (whole pyramid arrays and tipless pyramid arrays) using FDTD simulations and microbubble experiments. We then explore the laser parameter space to optimize... Read more about Subcellular surgery and nanosurgery
2D impedance-matched zero-index metamaterial, at SPIE Photonics West: Photonic and Phononic Properties of Engineered Nanostructures IV (San Francisco, California), Wednesday, February 5, 2014
Recent efforts to achieve metamaterials with a vanishing refractive index take advantage of the low index at a photonic band edge. This behavior is accompanied by a divergent impedance, resulting in inefficient transmission. We investigate the nature of this discontinuity and show that it can be removed by tuning the electric and magnetic response of the metamaterial. We present a design for a 2D zero-index metamaterial based on this concept. The metamaterial is entirely dielectric, which results in low-loss transmission at the design wavelength of 1.55um. This behavior is confirmed using... Read more about 2D impedance-matched zero-index metamaterial
Nonlinear refraction in rutile TiO2, at SPIE Photonics West: Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII (San Francisco, California), Tuesday, February 4, 2014
Titanium dioxide (TiO2) has attractive optical properties for nonlinear optical applications ranging from telecommunication to interconnect wavelengths (800–1600 nm). TiO2 demonstrates large linear and nonlinear refractive indices, wide transparency from the infrared to as low as 400 nm wavelengths, and low two-photon absorption for wavelengths longer than 800 nm. We use the Z-scan technique to investigate the nonlinear refraction and multiphoton absorption of bulk rutile TiO2 for wavelengths ranging from 800–1600 nm. Using our results, we calculate nonlinear figures of merit and discuss... Read more about Nonlinear refraction in rutile TiO2
Maximizing intensity in TiO2 waveguides for nonlinear optics, at Photonics West (San Francisco, California), Wednesday, February 6, 2013:
Titanium dioxide (TiO2) represents an attractive candidate for nonlinear optical devices due its high transparency, large refractive index, and large Kerr nonlinearity. Using electron beam lithography and a liftoff procedure, we can structure both amorphous TiO2 as well as polycrystalline anatase thin films to create photonic devices that exploit the material’s properties in order to do nonlinear optics. Nonlinear optics benefit from long interactions, necessitating large intensities along long waveguide lengths. For this reason, waveguide losses need to be minimized. We study the effects... Read more about Maximizing intensity in TiO2 waveguides for nonlinear optics
Hydrogenated amorphous silicon laser micromachining for photonic devices, at SPIE Photonics West 2013, Synthesis and Photonics of Nanoscale Materials X (San Francisco, CA), Tuesday, February 5, 2013
Abstract Development of integrated photonic devices is becoming increasingly important in technological applications. Hydrogenated amorphous silicon (a-Si:H) provides a promising platform. Variations in hydrogen content produce large changes in refractive index and band gap, on the order of 0.1-1. Previous research has demonstrated waveguide fabrication using photolithography and ion implantation techniques, which requires many steps and is limited to 2D patterns. We have developed a laser micromachining technique to locally reduce the hydrogen content of a-Si:H in the laser focus to... Read more about Hydrogenated amorphous silicon laser micromachining for photonic devices
Using Video Analysis to Classify Student Discussions During Peer Instruction, at American Association of Physics Teachers Winter Meeting 2013 (New Orleans, LA), Wednesday, January 9, 2013:
Numerous studies show courses taught using Peer Instruction have higher learning gains on standardized assessments. Yet we have very few measurements of what happens during the peer discussion component of this pedagogy. When students are told to discuss a physics question with a neighbor, do they do so? If so, do they have a substantive conversation about the physics, or just a brief exchange of answers? To address these questions, we recorded every student discussion in nearly every lecture of an introductory physics course at a major research university. Through both large-scale manual... Read more about Using Video Analysis to Classify Student Discussions During Peer Instruction