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

Daniel van de Weide
University of Wisconsin - Madison

Abstract
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 we’ve raised the photon energy so high that we will displace the electron, changing the object as we image it, a consequence of Heisenberg’s 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 circuit’s 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.

Bio
Daniel van der Weide received a BSEE from the University of Iowa in 1987, and a Master’s and Ph.D. in Electrical Engineering from Stanford University in 1989 and 1993, respectively.

He held positions with Lawrence-Livermore National Laboratory, Hewlett-Packard, Motorola and Watkins-Johnson Company. From 1993-95 he worked as a post-doctoral researcher with the Max-Planck-Institute for Solid State Research in Stuttgart, Germany, after which he joined the University of Delaware Department of Electrical & Computer Engineering as an assistant professor. There he was promoted to associate professor while founding and directing the Center for Nanomachined Surfaces. In 1999 he moved to the University of Wisconsin-Madison where he is a full professor in Electrical & Computer Engineering. He is a co-founder of Neuwave Medical Inc, Optametra LLC (acquired by Tektronix in July 2011) and Tera-X LLC.

Young Investigator Program Award - Office of Naval Research, 1998
PECASE Award - National Science Foundation, 1997
CAREER Award - National Science Foundation,1997
DARPA Ultra Electronics Program Outstanding Individual Technical Achievement Award, 1997
University Research Award - Ford Motor Company,1996-98