MIT.nano Seminar: Acoustic Waves in Nanometer-Thick Films: Sub-Terahertz Devices and Coupling to Optical, Electronic, and Power Domains
Building 12, 60 Vassar Street, Cambridge, MA
Ruochen Lu Assistant Professor, Chandra Family Department of Electrical and Computer Engineering The University of Texas at Austin Date: September 21, 2026 Time: 3:00 – 4:00 PM ET Location: 12-0168 Reception to follow. ABSTRACT Acoustic waves travel about five orders of magnitude slower than electromagnetic waves, so at the same frequency an acoustic wavelength is roughly 100,000 times shorter. That is why a modern smartphone holds more than eighty acoustic filters, and why piezoelectric devices are among the most volume-efficient signal processing components on chip. This talk asks how far that advantage can be scaled in piezoelectric platforms. In thin film piezoelectrics, e.g., lithium niobate, scaling toward millimeter-wave and sub-terahertz frequencies runs into two constraints that pull against each other: thinner films lose quality factor to surfaces and interfaces, while higher-order overtones lose piezoelectric coupling to charge cancellation. The first part of the talk covers periodically polarized piezoelectric films, in which bonded interfaces a few nanometers thick are placed at acoustic stress nodes so that the two constraints can be treated separately. On this…