Fiber laser based ultrasound sensor for photoacoustic imaging

Photoacoustic imaging, especially for intravascular and endoscopic applications, requires ultrasound probes with miniature size and high sensitivity. In this paper, we present a new photoacoustic sensor based on a small-sized fiber laser. Incident ultrasound waves exert pressures on the optical fiber laser and induce harmonic vibrations of the fiber, which is detected by frequency shift of the beating signal between the two orthogonal polarization modes in the fiber laser. This ultrasound sensor presents a noise equivalent pressure of tens of Pa over a ~50 MHz bandwidth. We demonstrate this new ultrasound sensor on an optical-resolution photoacoustic microscope. The axial and lateral resolutions are measured. The field of view is on the order of 1 millimeter in lateral directions. We further demonstrate its application in photoacoustic microscopy. The present fiber laser ultrasound sensor offers a new tool for all-optical photoacoustic imaging.