Microscopes for sub-visible frequencies: scanning the near field in the microwave through infrared with micromachined probes

Prof. Dr. Daniel van der Weide

Associate Professor
Electrical & Computer Engineering
The University of Delaware
140 Evans Hall
Newark, DE 19716-3130
(302) 831-8784 phone
(302) 831-1218 fax

How could we image an electron? Just take a picture of it. We would find, however, that the Rayleigh criterion limits how small an object we can resolve: it must be about half a wavelength in size. So shrink the wavelength. Now weve raised the photon energy so high that we will displace the electron, changing the object as we image it, a consequence of Heisenbergs uncertainty principle.

While we have learned through "squeezing" light that we can trade knowledge of position and momentum within the confines set by Heisenberg, could Rayleigh also be so accommodating? If we are willing to trade the parallel nature of conventional far field optics for serial image acquisition in the near field, the answer is yes. In this talk I will describe how we design, microfabricate and use near-field antennas and other sensors that also work as scanning force microscopes. These probes have cross-disciplinary applications: they can make images of an integrated circuits topography and local electric or magnetic fields, but they 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 with diodes at their tips can be used for imaging local temperature and topography or directly detecting local microwave and optical fields. These micromachined multifunctional probes are enabling us to do microscopy and spectroscopy at dimensions as much as 10-6 smaller than the wavelengths we use, shedding quite literally a new light onto the microscopic world.