An Electrically Injected and Solid State Surface Acoustic Wave Phonon Laser

TL;DR

This paper introduces the first solid-state, single-chip surface acoustic wave (SAW) phonon laser with electrical injection, demonstrating coherent high-frequency acoustic output suitable for miniaturized, high-performance SAW systems.

Contribution

It presents a novel, fully integrated SAW phonon laser with electrical injection, enabling high-frequency, coherent acoustic generation on a compact chip.

Findings

Achieved 1 GHz continuous acoustic output power of -6.1 dBm

Demonstrated linewidth narrowing to less than 77 Hz

Showed potential for mHz linewidths and sub -100 dBc/Hz phase noise

Abstract

Surface acoustic waves (SAWs) enable a wide array of technologies including RF filters, chemical and biological sensors, acousto-optic devices, acoustic control of microfluidic flow in lab-on-a-chip systems, and quantum phononics. While numerous methods exist for generating SAWs, they each have intrinsic limitations that inhibit performance, operation at high frequencies, and use in systems constrained in size, weight, and power. Here, for the first time, we present a completely solid-state, single-chip SAW phonon laser that is comprised of a lithium niobate SAW resonator with an internal, DC electrically injected and broadband semiconductor gain medium with $<$0.15 mm$^2$ footprint. Below the threshold bias of 36 V, the device behaves as a resonant amplifier, and above it exhibits self-sustained coherent oscillation, linewidth narrowing, and high output powers. A continuous on-chip acoustic output power of up to -6.1 dBm is generated at 1 GHz with a resolution-limited linewidth of $<$77 Hz and a carrier phase noise of -57 dBc/Hz at 1 kHz offset. Through detailed modeling, we show pathways for improving these devices' performance including mHz linewidths, sub -100 dBc/Hz phase noise at 1 kHz, high power efficiency, footprints less than 550 um$^2$ at 10 GHz, and SAW generation approaching the hundreds of GHz regime. This demonstration provides a fundamentally new approach to SAW generation, paving the way toward ultra-high-frequency SAW sources on a chip and highly miniaturized and efficient SAW-based systems that can be operated without an external RF source.