Nonlinear thermo-acoustic phase modulator for physical reservoir computing
Taiki Ijima, Claude Meffan, Masaki Shimofuri, Amit Banerjee, Jun Hirotani, Toshiyuki Tsuchiya · Japanese Journal of Applied Physics · 2025
Abstract This study proposes a nonlinear thermo-acoustic phase modulator for application in physical reservoir computing. We designed and fabricated the modulator, and then investigated the properties such as insertion loss and modulation effects. Finally, we constructed a physical reservoir system with the proposed modulator and demonstrated benchmark tasks. The modulator makes use of surface acoustic waves, which contributes to fast processing and low power consumption. The modulator has a waveguide which also acts as a microheater. The modulation principle is a wave-velocity reduction caused by heating the surface of the substrate with the microheater, which provides nonlinearity and short-term memory required for the reservoir system. We confirmed these characteristics in the measurements of the modulator, and we verified the effectiveness of the modulator in the reservoir system with 2.3 of memory capacity in short-term memory task and 0.066 of normalized mean square error in NARMA2 task.