Nonlinear exceptional points in an integrated acoustic-wave oscillator for longwave infrared sensing

TL;DR

This paper demonstrates that a nonlinear exceptional point in an integrated acoustic-wave oscillator significantly enhances longwave infrared sensing performance, including responsivity, bandwidth, and noise characteristics.

Contribution

The study introduces a nonlinear EP in an acoustic oscillator for LWIR detection, showing substantial improvements over non-EP operation in practical sensing conditions.

Findings

33-fold increase in responsivity at EP

8.75-fold extension of 3-dB bandwidth at EP

6-fold enhancement in signal-to-noise ratio at 6.2 kHz

Abstract

Exceptional points (EP) featuring enhanced responsivity and rich dynamics have attracted extensive attentions in device developments and sensing applications. However, it remains debated whether employing EP systems is beneficial in practical sensing applications. Here, we demonstrate that a nonlinear EP in our microwave-frequency acoustic-wave oscillator improves longwave infrared (LWIR) detection under practical conditions. By phase tuning the nonlinear gain, our detector can be operated at different conditions with respect to the nonlinear EP. Compared with operation away from EP, our detector at EP shows a 33-fold improvement in responsivity and an 8.75-fold extension of 3-dB bandwidth. We observe a 6-fold enhancement in signal-to-noise ratio at an input modulation frequency of 6.2 kHz. At the incident LWIR wavelength of 9.6 um, our detector at EP exhibits a noise equivalent power (NEP) of 310 pW*Hz^-1/2 at input frequency of 10 kHz, yielding a figure of merit, product of NEP and time constant, of 9.87*10^-3 pW*Hz^-3/2, a 10-fold improvement over operation away from EP. Our integrated acoustic devices offer a versatile platform for exploring noise dynamics and developing practical sensors that exploit non-Hermitian nonlinearities.