My group designs, build and use microfabricated circuits and structures for high frequency probes and sensors with an eye toward cross-disciplinary applications. Though all our instruments work somewhere in the DC-THz frequency range, many are proximal probes, scanned at or very near a sample, while others measure a collective response in the far field, at distances much greater than the wavelengths they use.
Some of the proximal probes are tiny antennas that can be used with scanning probe microscope platforms to make images of an integrated circuit?s topography and local electric or magnetic fields. These same probes can also be used to examine sub-surface defects in materials such as silicon and quartz, excite "artificial molecules" made with semiconductor quantum dots, probe moisture content in paper fibers, and perhaps map out the structure and dynamics of ion channels in neuronal membrane. Other probes using diodes at their tips can be used for imaging local temperature and topography or directly detecting local microwave and optical fields.
The far-field sensors we are developing are based on picosecond-pulse electronic circuits using nonlinear transmission lines and integrated antennas. We are currently using GaAs versions of these circuits for measuring components of automotive exhaust gasses and for making reflection spectra of explosives and weapons for aviation security. We are also designing complete integrated-circuit coherent measurement systems to drive these circuits, and we are investigating less expensive silicon realizations of these sensors and systems.
Finally, we are pursuing ways of sharing these instruments through the Web, using remote-accessed instrumentation for educational outreach and experimental collaboration.