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. (Figure presented.).