Single-wavelength sO₂ measurement based on Grüneisen-relaxation photoacoustic effect

The photoacoustic effect-based sO₂ measurement is attracting more and more attention due to its non-invasiveness and accuracy. Compared with the linear dual-wavelength method, the sO₂ measurement based on single-wavelength excitation can be potentially applied with simplified system construction. However, the single-wavelength methods proposed in previous studies decreases the safety or lacks the in-depth resolution. This paper proposes a novel single-wavelength method based on the Grüneisen-relaxation (GR) nonlinear effects. It avoids the high fluence excitation with maintaining in-depth resolution and obtains the signals in hundreds of nanoseconds, simultaneously improving the safety and detection speed. The construction of a single laser source for GR effect generation makes the system stable. The sO₂ quantification results of blood samples have a good consistency with the reference values. Our work provides a safer and faster measurement method, and a stable system, to promote its application in the clinical area.