Breaking sensitivity limits of optical ultrasound sensors used in photoacoustic imaging

The impact of optical absorption in the spacer layer of Fabry-Perot (FP) ultrasound sensors is discussed. It is shown that absorption significantly limits the sensitivity of planoconcave microresonators (PCMRs; FP type sensors with a planoconcave geometry). Using materials of lower absorption or selecting sensor interrogation wavelengths to avoid absorption peaks in existing spacer materials could provide at least an order of magnitude higher sensitivity, paving the way to multi-cm deep-tissue PA imaging applications.