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 platform we have measured resonators above 200 GHz and filters up to 50 GHz. Cryogenic measurements separate temperature-dependent phonon–phonon dissipation from the temperature-independent interface loss that dominates at present, and show that these devices are still well short of the intrinsic limit.
Additionally, thin suspended films also concentrate energy, so modest drive powers are enough to produce strong nonlinearity, including phononic frequency combs generated from a single input tone. The talk closes with ways the same platform couples acoustics to other domains: optomechanical infrared sensing, acoustoelectric interaction with electrons, and piezoelectric resonators that replace magnetics in power conversion. Taken together, these devices cover nearly six decades of frequency, from ultrasonic transducers below 100 kHz to resonators above 100 GHz, on one integrated acoustic microsystems.
BIOGRAPHY
Ruochen Lu is an Assistant Professor of Electrical and Computer Engineering at The University of Texas at Austin, where he leads the Resonant Acoustic Microsystems (RAM) Lab. He received the B.E. in microelectronics from Tsinghua University in 2014 and the Ph.D. in electrical engineering from the University of Illinois Urbana-Champaign in 2019.
His group develops thin-film piezoelectric MEMS and acoustic microsystems, including resonators and filters spanning microwave to sub-terahertz frequencies, ultrasonic transducers, nonlinear phononics, piezoelectric power conversion, and the heterogeneous integration of acoustics with electronic, photonic, magnetic, and quantum systems.
He received the IEEE MTT-S Microwave Prize in 2022, the IEEE Ultrasonics Early Career Investigator Award and the NSF CAREER Award in 2024, and the Transducer Research Foundation Rising Star of Microsystems Award in 2026. He is an associate editor for IEEE JMEMS, IEEE Transactions on Ultrasonics, IEEE Journal of Microwaves, and IEEE Electron Device Letters.