Presentations

    Optoelectronic devices using femtosecond laser microstructured silicon, at NATO ASI Course on New developments in optics and related fields: modern techniques, materials, and applications, Centro Ettore Majorana (Erice, Italy), Sunday, June 12, 2005:
    Arrays of sharp, conical microstructures are obtained by stucturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless structuring process drastically changes the optical, material and electronic properties of the original silicon wafer. These properties make microstructured silicon viable for use in a wide range of commercial devices including solar cells, infrared photodetectors, chemical and biological sensors, and field emission devices.
    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)
    Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering, 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
    Femtosecond laser-nanostructured substrates for single molecule surface-enhanced Raman spectroscopy, at Photonics West (San Jose, California), Tuesday, January 22, 2008:
    We present a new type of surface-enhanced Raman scattering (SERS) substrate that exhibits extremely large and uniform cross-section enhancements over a macroscopic (>25mm2) area. The substrates are fabricated using an extremely simple procedure: a train of femtosecond laser pulses is used to structure a silicon wafer with an array of submicron-sized spikes, and a silver film is subsequently deposited on the structured surface. SERS signals from adsorbed molecular dyes indicate a spatially uniform enhancement factor (ca. 10^7) that is consistently observed over a wide range of excitation... Read more about Femtosecond laser-nanostructured substrates for single molecule surface-enhanced Raman spectroscopy
    Isolating surface-enhanced Raman scattering hot spots using surface-enhanced multiphoton lithography, at Photonics West 2010 (San Francisco, CA), Monday, January 25, 2010:
    We present a method for improving femtomole-level trace detection (10^9 molecules) using large-area surface-enhanced Raman scattering (SERS) substrates. Using multiphoton-induced exposure of a commercial photoresist, we physically limit the available molecular adsorption sites to only the electromagnetic “hot spots” on the substrate. This process prevents molecules from adsorbing to sites of weak SERS enhancement, while permitting adsorption to sites of extraordinary SERS enhancement. For a randomly adsorbed submonolayer of benzenethiol molecules the average Raman scattering cross section of... Read more about Isolating surface-enhanced Raman scattering hot spots using surface-enhanced multiphoton lithography
    Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection, at Stanford University (Stanford, CA), Tuesday, January 26, 2010:
    Surface-enhanced Raman scattering (SERS) is one of the most sensitive molecular spectroscopy techniques currently available. Using SERS, it is possible to obtain vibrational spectra from chemical quantities as small as a single molecule. However, it is challenging to have molecules of interest adsorb specifically to a substrate’s “hot spots,” or regions of largest electromagnetic enhancement. I will describe a nonlinear optical technique that masks SERS substrates such that only hot spots are available as molecular adsorption sites. Using this approach, we have demonstrated a 27-fold... Read more about Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection
    Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection, at Northwestern University (Evanston, IL), Thursday, February 25, 2010
    Surface-enhanced Raman scattering (SERS) is one of the most sensitive molecular spectroscopy techniques currently available. Using SERS, it is possible to obtain vibrational spectra from chemical quantities as small as a single molecule. However, it is challenging to have molecules of interest adsorb specifically to a substrate’s “hot spots,” or regions of largest electromagnetic enhancement. I will describe a nonlinear optical technique that masks SERS substrates such that only hot spots are available as molecular adsorption sites. Using this approach, we have demonstrated a 27-fold... Read more about Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection
    Plasmon-enhanced ultrafast laser cell transfection, at Photonics West 2011 (San Francisco, CA), Sunday, January 23, 2011:
    We present a method for transfecting biological cells using ultrafast plasmons excited on large areas of bio-compatible, nano-pyramid substrates. This technique does not employ any potentially toxic chemical transfection reagents or metallic nanoparticles. Leveraging the field enhancement supported by these pyramidal plasmonic nanostructures, we generate localized, transient pores in the membranes of large numbers of cells at a rate of approximately 10^4 per second. Diffusion through these pores enables the delivery of functional short interfering RNA (siRNA) molecules into the cells. We... Read more about Plasmon-enhanced ultrafast laser cell transfection
    Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection, at UCLA IEEE photonics society seminar, University of California, Los Angeles (Westwood, CA), Thursday, February 4, 2010:
    Surface-enhanced Raman scattering (SERS) is one of the most sensitive molecular spectroscopy techniques currently available. Using SERS, it is possible to obtain vibrational spectra from chemical quantities as small as a single molecule. However, it is challenging to have molecules of interest adsorb specifically to a substrate’s “hot spots,” or regions of largest electromagnetic enhancement. I will describe a nonlinear optical technique that masks SERS substrates such that only hot spots are available as molecular adsorption sites. Using this approach, we have demonstrated a 27-fold... Read more about Nonlinear plasmonics: SERS hot spot isolation and enhanced laser cell transfection