Dr. David Bruce Burckel: Sandia National Laboratories
Abstract: Bulk optical materials like glasses and semiconductors (for infrared appli-cations) have continuous translational symmetry on the scale of the design wavelength, and hence support a continuum of allowed modes with frequency dependent optical constants dictated by the material dispersion relationship. Much of the recent progress in optical materials has been driven by periodic structuring of materials on finer and finer scales relative to the design wave-length. Recently metasurface optics employing planar plasmonic structures ar-rayed in a two-dimensional (2D) array to affect beam steering and lensing were reported. Subsequent analysis of the physical mechanisms at play revealed that such a planar system has a maximum theoretical efficiency of 25%. The analysis further showed that by enabling current flow in the third dimension, the direction of travel through the lens, this restriction could be lifted.
In this seminar, I will discuss our recent work on fabrication and characterization of 3D meta-films, suspended structures with sub-wavelength structuring along all three dimensions and a total thickness of < 4-μm. The struc-tures are fabricated on ~ 1-μm thick silicon nitride membranes using a new CMOS compatible membrane pro-jection lithography (MPL) approach. Elimination of the bulk substrate allows us to collect almost all the transmit-ted and reflected light from the sample and simplifies modeling and design. The response of these 3D meta-films possesses features characteristic of the metallic meta-atoms as well as slab photonic crystal resonances resulting from the periodic unit cell array, the nitride walls and support membrane. I will outline the fabrication sequence and present measured infrared transmission characterization of 3D unit cells with vertically oriented elliptical plasmonic inclusions in the unit cell. Furthermore, we demonstrate control over the coupling between the plasmonic modes of the metallic inclusion and photonic crystal slab modes of the support matrix by adjusting the dimensions of the inclusions. The ability to control the coupling between the unit cell decoration and the unit cell matrix while also allowing for current flow in all three dimensions offers a powerful new design element for next generation optical elements.
Bio: Bruce Burckel received his BS in Electrical Engineering from the University of New Mexico in 1993, at which point he was evenly split between attending graduate school, medical school or law school. Graduate school won out, probably costing him millions of dollars in lifetime earnings, but he is only mildly bitter about this. He received his MS (1995 – optical non-contact temperature measurement) and PhD (2004 – generalized transverse Bragg waveguiding) also from the University of New Mexico, separated by a stint contemplating a software start-up, studying control system theory, designing space-based relay mirror telescopes and studying atmospheric propagation for high power laser applications. Although his PhD was centered on photonic applications of interferometric lithography at the micro and nano-scale, he secured a Post-Doctoral position in an inorganic chemistry lab studying self-assembled nanocomposite coatings. He is currently a Principal Member of the Technical Staff at Sandia National Laboratories, where he leads several efforts in micron-scale 3D fabrication and structured electromagnetics. He is frequently found counseling students on the importance of career planning, as well as studying for the LCAT in local coffee shops.
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