Contributed

Reducing the gender gap in introductory physics, at American Physical Society March meeting (Denver, CO), Monday, March 5, 2007:
We investigated whether the gender gap in conceptual understanding in an introductory university physics course can be reduced by teaching with interactive engagement methods that promote in-class interaction, reduce competition, foster collaboration, and emphasize conceptual understanding. To this end, we analyzed data from the introductory calculus-based physics course for non-majors at Harvard University taught traditionally or using different degrees of interactive engagement. Our results show that teaching with certain interactive strategies not only yields significantly increased... Read more about Reducing the gender gap in introductory physics
Efficient coupling between guided optical modes in ZnO nanowire-waveguides and tapered silica fibers, at Photonics West 2007 (San Jose, CA), Thursday, January 25, 2007:
We combine top-down and bottom-up processes for the fabrication of photonic nanowires to efficiently inject and extract light from waveguide modes of ZnO nanowires lying on low refractive index silica aerogel substrates. Our approach relies on the emission of propagating modes of the light field from a tapered silica fiber and the efficient coupling of the emitted field into the high-index ZnO nanowires. We show that this approach provides a robust and surprisingly efficient technique to study the waveguiding properties of semiconductor nanowires. The experimental results are confirmed and... Read more about Efficient coupling between guided optical modes in ZnO nanowire-waveguides and tapered silica fibers
Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering (SERS), at Photonics West 2007 (San Jose, CA), Thursday, January 25, 2007:
We present a new substrate for efficient surface enhanced Raman scattering (SERS). Using a train of focused frequency-doubled femtosecond laser pulses from a regeneratively amplified Ti:Sapphire laser, we fabricate submicron surface structures on a silicon wafer. After irradiating the silicon wafer with 400nm, 100fs laser pulses in a cuvette of water, we observe the formation of an array of spikes, each approximately 500nm tall and 200nm wide. The wafer is scanned across the beam to form an arbitrarily-sized nanostructured area. When covered with a thin film of a noble metal, the structured... Read more about Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering (SERS)
Applications of femtosecond laser ablation for nanoneurosurgery in C. elegans., at Photonics West 2007 (San Jose, CA), Saturday, January 20, 2007:
We ablate cellular material with submicrometer resolution using tightly-focused, 2-5 nJ femtosecond laser pulses. Due to the nonlinear absorption of laser light, the disruption occurs within the bulk of the sample without incision. The low energy of the pulses minimizes collateral damage. The technique has broad applicability because any optically resolvable structure within the working distance of a high-NA objective can be disrupted. Current applications of this technique include probing cytoskeletal mechanics, imaging brain tissue, and investigating the neurobiology of the nematode worm C... Read more about Applications of femtosecond laser ablation for nanoneurosurgery in C. elegans.
Two-photon engineered polymer scaffolds for 3D migration studies, at MRS Fall Conference 2006 (Cambridge, MA), Wednesday, November 29, 2006
In tissue engineering, control of ligand-receptor-mediated interaction between cell and material is an underlying principle for designing biomaterials. Microfabrication techniques such as soft lithography have enabled researchers to study cell behavior extensively in two dimensions (2D) by controlling the spatial distribution of ligands on a micrometer and sub-micrometer scale. However, lack of an appropriate three-dimensional (3D) microfabrication technique with micrometer resolution has prevented from presenting cell adhesion ligands in an organized fashion in 3D. Thus, fabricating such a... Read more about Two-photon engineered polymer scaffolds for 3D migration studies
Can Students Evaluate Their Own Understanding?, at AAPT Summer Meeting (Syracuse, NY), Tuesday, July 25, 2006:
Can students assess their own understanding in introductory physics? How does their assessment change during the learning process? Instructors often gauge how well students are assimilating the material based on the number of questions or confused looks they receive during their interactions with students. However, it is unclear how well students are able to recognize their own understanding (or lack thereof). In this talk, we present preliminary results from our study of the relationship between students' perceived understanding and their actual understanding of introductory physics concepts... Read more about Can Students Evaluate Their Own Understanding?
Three-dimensional microfabrication for photonics and biomedical applications, at Macro 2006 - World Polymer Congress (Rio de Janeiro, RJ, Brazil), Sunday, July 16, 2006:
We use two-photon absorption polymerization to fabricate microstructures containing compounds with interesting properties for optical and biomedical applications. Our investigations open the door to new applications in data storage, waveguides manufacturing, organic LEDs, optical circuitry and scaffold for bio-applications.
Supercontinuum in silica nanowires, at Photonics West 2006 (San Jose, CA), Thursday, January 26, 2006:
Fibers are gaining widespread acceptance for generating ultra-broad spectra. The most common approach involves a photonic crystal fiber with carefully designed core size and dispersion characteristics. Although this system provides confinement of light to micrometer (and sometimes sub-micrometer) dimensions, this confinement is achieved at the expense of a complex core structure. An alternative to microstructured fibers is the use of silica fibers with sub-wavelength diameters whose waveguiding properties were initially demonstrated by our group. Silica nanowires are a model system because... Read more about Supercontinuum in silica nanowires
Femtosecond micromachining of waveguides in a Faraday material, at Photonics West 2006 (San Jose, CA), Tuesday, January 24, 2006
The use of femtosecond lasers for micromachining purposes has grown significantly over the past decade. Femtosecond micromachining of photonic devices has been demonstrated using only a few nanojoules of energy from a laser oscillator. This oscillator-only technique has recently become increasingly valuable as a micromachining tool.

Faraday isolators have not yet been realized using this ultrafast micromachining technique. A Faraday isolator is an important device because it functions as an optical diode, allowing signals to propagate only in one direction. It is particularly useful in...

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