The Optics Laboratory

Group of Hans Hallen, North Carolina State University Physics Department

 Near-Field Scanning Optical Microscopy: An Introduction

We have been leaders in the development of all aspects of NSOM for several years. See what we and other groups have been up to in this emerging field with this tutorial style introduction.

 Near-Field Raman Spectroscopy: Resolution, Selection Rules, Etc.

Raman spectroscopy through a near-field aperture differs from conventional Raman in more ways than better spatial resolution. The selection rules differ, the Rayleigh tail background is lower, the surface signal is enhanced, and we obtain a simultaneous topographic image. See also the first nano-Raman Images and cartoons of what Raman spectroscopy is (for the un-initiated).

 Gradient-Field Raman: A New Spectroscopy

When a near-field aperture is used for Raman spectroscopy, strong gradients of the electric field strength cannot be ignored. The origin of the spectra must be re-derived, and interesting properties (including measurable signal) elucidated.

 Oxygen in YBCO, Stability and Probe Induced Electromigration

Oxygen can move in the high temperature superconductor YBCO. It can move in time causing aging -- we image that with nano-scale resolution and correlate to the topography, or it can be pushed by an electric current -- electromigration. The changes in oxygen content alter the superconducting properties, so these considerations are important in reliability and lifetime estimates. We supply a current with our probe, and quantify the effects in samples provided by Brian Moeckley (Conductus) and others.

 Wireless Communications: The Physics of Channel Fading

Did you ever experience a radio station that chopped in and out as your car moved? The same thing happens with wireless phones. This is a new approach to combat these rapid signal power variations in digital wireless, based on physical models and communications algorithms. This work is in collaboration with Alexandra Duel-Hallen's group in Electrical and Computer Engineering.

 Nano-Scale Mapping of Carrier Lifetime: Quantitation, Resolution

We developed an all-optical, nanoscale-resolution imaging method for semiconductor characterization. Carrier lifetime can be quantitatively measured over several orders of magnitude. See how we do it and consider how it is possible (it is) to get resolution better than the average distance the carriers move in the measurement time.

 Nano-Scale BioProbes: Dissecting Signal Pathways (Under Construction)

This collaboration with Nina Stromgren Allen's Laboratory in Botony uses our proximal probe tips and their functional imaging microscopy to open a new venue to signal pathway studies.

 Nonlinear Effects Near a Metal Proximal Probe (Under Construction)

The lightning rod effect is important near any sharp metal point, such as our probe tips. We make use of this to localize interface measurements in three dimensions, in addition to some other tricks …

 Atmospheric Aerosols: Close-Up and Far Away (Under Construction)

Submicron particles in the air are bad for you, as the EPA has shown. How do they effect health and how do we measure their location, density and properties at a given time? This program in collaboration with Russell Philbrick's group at Penn state seeks answers to these questions.

 Students Involved:

Graduate Students

Current Undergraduate Students

 Some Papers.

 Funding Provided by: Office of Naval Research, Army Research Office, National Science Foundation, Center for Advanced Computers and Communications, Teledyne Lighting and Display Products, and NCSU.

NC State University | Physics | Optics Home

Last updated on June 14, 2002
Copyright ©1999-2002,
Hallen Laboratory, NCSU, Raleigh, NC.
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