In 1880, American scientist Alexander Graham Bell discovered that when a material is irradiated with modulated light, it absorbs the light and generates acoustic signals at the same frequency as the incident light modulation. The signal intensity increases with greater light absorption by the material. However, constrained by the technological limitations of that era—particularly the lack of powerful light sources and sensitive detectors—this discovery did not lead to immediate advancements.

The 1960s witnessed renewed interest in the photoacoustic effect with the advent of lasers and the development of highly sensitive microphones and piezoelectric transducers. Nevertheless, progress remained relatively slow. It was not until the 1990s that photoacoustic imaging (PAI) technology, based on the photoacoustic effect, experienced rapid development and found widespread applications in biomedical fields. Pulsed laser-based PAI enables high-resolution, high-contrast imaging of biological tissues, making it an exceptional technology for applications in biological imaging, dermatological imaging, molecular imaging, and functional imaging.

Currently, PAI has reached its highest level of maturity in biomedical imaging. In vascular imaging, for instance, hemoglobin’s absorption characteristics at wavelengths such as 532 nm and 1064 nm make Q-switched Nd:YAG pulsed lasers ideal for high-contrast imaging of vascular structures, even in deep tissues. RealLight‘s microchip pulsed lasers, with their nanosecond pulse widths, further enhance spatiotemporal resolution in PAI applications. Their high peak power ensures sufficient energy for signal excitation, while their compact design facilitates the development of low-cost, portable PAI devices. In tumor detection, PAI can identify abnormal blood oxygen metabolism in tumor regions. Similarly, in brain imaging, it is used to study cerebral vascular networks and hemodynamics.

In summary, pulsed lasers serve as the core light source for PAI. Their high peak power and ultrashort pulse characteristics make them indispensable for biomedical imaging, molecular imaging, and functional imaging. As laser technology and imaging algorithms continue to advance, the applications of pulsed lasers in PAI will expand further, driving deeper innovations in the field.

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