The addition of active, nonlinear, and nonreciprocal functionalities to passive piezoelectric acoustic wave technologies could enable all-acoustic and therefore ultra-compact radiofrequency signal processors. Toward this goal, we present a heterogeneously integrated acoustoelectric material platform consisting of a 50 nm indium gallium arsenide epitaxial semiconductor film in direct contact with a 41° YX lithium niobate piezoelectric substrate. We then demonstrate three of the main components of an all-acoustic radiofrequency signal processor: passive delay line filters, amplifiers, and circulators. Heterogeneous integration allows for simultaneous, independent optimization of the piezoelectric-acoustic and electronic properties, leading to the highest performing surface acoustic wave amplifiers ever developed in terms of gain per unit length and DC power dissipation, as well as the first-ever demonstrated acoustoelectric circulator with an isolation of 46 dB with a pulsed DC bias. Finally, we describe how the remaining components of an all-acoustic radiofrequency signal processor are an extension of this work.
This work presents a 3-Port acoustoelectric switch design for surface acoustic wave signal processing. Using a multistrip coupler, the input acoustic wave at Port 1 is split into two parallel and electrically cross-linked acoustoelectric delay lines where an applied voltage can alter the gain and attenuation in each delay line based on the voltage polarity. The switch is demonstrated using a 270 MHz Leaky SAW mode on an InGaAs on 41° Y-cut lithium niobate heterostructure. Applying a +40 V voltage pulse results in an IL of -12.5 dB and -57.5 dB in the gain and isolation switch paths, respectively. This leads to a 45 dB difference in signal strength at the output ports.
We present the design, fabrication, and initial characterization of a CMOS compatible, ultra-high bandwidth, bulk-micro machined, optomechanical accelerometer. Displacement detection is achieved via a SiN integrated photonics Mach-Zehnder interferometer (MZI) fabricated on the surface of the device that is optomechanically coupled to acceleration-induced deformation of the accelerometer's proof mass tethers. The device is designed to measure vibrations at microsecond timescales with high dynamic range for the characterization of shock dynamics.
Radio frequency (RF) devices are becoming more multi-band, increasing the number of filters and other front-end components while simultaneously pushing towards reduced cost, size, weight, and power (CSWaP). One approach to reducing CSWaP is to augment the achievable functionalities of electromechanical/acoustic filtering chips to include "active" and nonlinear functionalities, such as gain and mixing. The acoustoelectric (AE) effect could enable such active acoustic wave devices. We have examined the AE effect with a leaky surface acoustic wave (LSAW) in a monolithic structure of epitaxial indium gallium arsenide (In GaAs) on lithium niobate (LiNb0 3 ). This lead to experimentally demonstrated state-of-the-art SAW amplifier performance in terms of gain per acoustic wavelength, reduced power consumption, and increased power efficiency. We quantitatively compare the amplifier performance to previous notable works and discuss the outlook of active acoustic wave components using this material platform. Ultimately, this could lead to smaller, higher-performance RF signal processors for communications applications.