Numerical investigations on phase-diversity optical digital coherent receiver-based noncontact photoacoustic signal detection

Abstract

Optical interferometry is promising for noncontact photoacoustic (PA) signal detection; however, the intensity detection of the interference signal makes the system insensitive and unreliable due to fluctuations in the optical path length difference. To address this, a noncontact PA signal detection utilizing an optical digital coherent receiver to acquire the entire quadrature components of the PA signal in self-homodyne mode is proposed and numerically investigated. Simulation results show that by applying a narrow bandwidth probe laser at a linewidth of 33 kHz, the signal SNR meets the requirement of a 12-bit quantizer together with 13-dB tolerance to extra-intensity noise.

Non-contact sub-nanometer displacement sensing based on optical digital coherent detection using frequency-domain filters

“…Here, κ represents the wave number, and the factor of 2 considers the round-trip propagation of the detection light to the sidewall of the piezoelectric actuator. As observed in the graph, due to fluctuations in OPD, the phase difference between the two optical paths causes slow variations in the baseline of the calculated raw displacement[26,27].…”

“…Additionally, the loss of initial phase information in cross-correlation techniques makes it challenging to apply them to real-time detection [21,22]. To overcome these challenges, a novel displacement sensing method based on phase-diversity optical digital coherent detection [23][24][25] has recently been introduced [26][27][28]. This method reconstructs displacement information by capturing the in-phase (I) and quadrature (Q) components of the signal.…”