Monolithically integrated passive photonic silicon chip for nano-g level acceleration tri-axial detection

This paper proposes a nano-g level monolithically integrated tri-axial passive photonic accelerometer chip using uniform silicon-based micromachining with a low-frequency band. The silicon sensing units are designed with compact gradient-type and asymmetric S-type spring beams, allowing superior sensitivity in low-frequency band and tri-axial consistency. The spring-mass structures behave with uniform 460 μm thickness, significantly simplifying the silicon micromachining and improving process yield. A fiber-based Fabry-Perot interferometer (FPI) is utilized to retrieve the acceleration signal by demodulating optical phase change. In the operating bandwidth of 1 to 80 Hz, the sensitivity of the X-axial and Y-axial sensing units surpasses 43.6 dB with linear responses, while the Z-axial unit exhibits a sensitivity of over 42.8 dB. The average minimum detectable accelerations (MDAs) of the tri-axis directions are measured to be 21.80 ng/Hz^1/2, 24.77 ng/Hz^1/2, and 32.47 ng/Hz^1/2, with the transverse crosstalk below 1.32%, 1.43%, and 2.07%, respectively. These results show that the proposed tri-axial photonic accelerometer is a perspective for detecting low-frequency acceleration vector signals.