EE298-5, Spring 2010
Photonics and Plasmonics Seminar
Fridays: 11:00 am - 12:30 pm
An interest in Photonics and/or Plasmonics.
May be taken for credit and/or fun.
No text required.
Seminar Schedule (pdf)
Seminar Schedule with Abstracts and Bios (pdf)
THIS WEEK'S SEMINAR
Professor Ivan P. Kaminow
254M Cory Hall
Phone: (510) 642-4867
254M Cory Hall
This course has no TA.
Back to Top
- May 7, 2010
11:00 am - 12:30 pm
521 Cory Hall
ADAM SCHWARTZBERG, Molecular Foundry at LBNL
Highly-Efficient Upconversion and Directional Nanoscale White-Light Generation in Gallium Nitride Nanowires
The generation and control of directional white light is critical for many technological, spectroscopic, and imaging applications. On the millimeter or greater scale, it may be attained and manipulated via high-energy pumping followed by phosphorescence, however, there currently exists no general method to generate and direct white light at nanoscale dimensions due to dual limitations of inevitable sample damage and demanding fabrication requirements. In this talk I will discuss the first facile method of generating directional, broadband, nanoscale white-light. This is achieved by highly-efficient upconversion of low-energy, sub-bandgap, continuous-wave (CW) 532nm illumination in sub-wavelength diameter Gallium Nitride (GaN) wires followed by cascading emission at excitation powers orders of magnitude below what is nominally required for such a process. Directed emission of this white light results from the high dielectric constant and large aspect ratio of these wires, which collectively create a low-loss (Q~200) light guiding cavity. We subsequently employ this unique directed white light source to perform interferometry on individual nanowires, and analyze the optical modes which develop due to internal reflection between the faceted ends of the wire. Interestingly, this directed nanoscale white light source has revealed new physics—significant variation in refractive indices from wire to wire, with many deviating significantly from bulk values. These unexpected refractive index values, precisely obtained by single-wire interferometry, also show remarkable power-dependent threshold behavior. Such power-threshold behavior for optical constants is diagnostic of the onset of multiphoton processes, such as parametric upconversion, which are clearly operative in these nanowires. Discovery of such an inexpensive, energy-efficient route to generation and piping of broadband visible light creates new opportunities in spectroscopy and analytical metrology. I will also discuss our recent results with near field plasmonic imaging of carbon nanotubes and future research directions.
Adam Schwartzberg received his PhD from the University of California at Santa Cruz where he worked on surface enhanced Raman scattering (SERS) and rational metal nanoparticle design and synthesis with Professor Jin Z. Zhang. During this time he also worked at Lawrence Livermore National Lab as a graduate research fellow with Professor Thomas Huser developing and characterizing single nanoparticle SERS sensing substrates. Adam's first postdoctor fellowship was with Professor Stephen R. Leone at UC Berkeley working on broad-band coherent anti-Stokes Raman scattering (BBCARS) for imaging and characterization of biological and e-beam resist materials. Adam is currently at the Molecular Foundry at Lawrence Berkeley national labs working with Dr. Jeffrey Urban studying the directed generation of white light in gallium nitride nanowires and using near field optical microscopy to study band structure and interfacial dynamics in low dimensionality nano-heterojunctions (<5 nm).