A novel fiber optical parametric oscillator for high-contrast and high-speed photoacoustic imaging of water

With the deepening of the research on the long-wavelength optical imaging of the near-infrared window, the requirements for the excitation laser source are increasing as well. As one of the important substances in the composition of life, water-related imaging work has been rarely reported because there is no suitable excitation laser light source and imaging method. To solve this problem, we demonstrated a fiber-based optical parametric oscillator called hybrid optical parametrically-oscillating emitter (HOPE) source operated at 1930 nm for photoacoustic imaging (PAI) of water, where the highest absorption peak of the O-H band in the NIR window locates. However, due to the limitation of optical signal-to-noise ratio and underperforming parameters in the time domain, it greatly limits imaging contrast and speed. Here, a new HOPE is demonstrated with improved parameters, which could be combined with PAI for water content imaging with high contrast and speed. Further, we explore and discuss the potential of water as a contrast in the PAI.