Fig. 1. (a) Schematic of the all-fiber ultrasound probe. The probe generates ultrasound pulses and detects pulse-echo signals to have an A-line. It scans transversely (along the x axis) to form a 2D image (B-scan). (b) A schematic and SEM image of the fiber-end-face ultrasound generator. (c) A schematic and photograph of the fiber-laser ultrasound sensor. The fiber segment emitting green fluorescent light is the Er/Yb-codoped fiber. It contains a laser cavity defined by two wavelength-matched Bragg reflectors.

Fig. 2. Acoustic characterization. (a) The recorded ultrasound signal and (b) its acoustic spectrum. (c) The measured acoustic pressure versus the light pulse energy. The ultrasound pressure significantly dropped at 2.5 μJ as a result of the damage of the absorptive medium. (d) The recorded echo signal. (e) The calculated frequency response.

Fig. 3. Phantom result. (a) A schematic of imaging a wire phantom that consists of eight spatially assembled silica fibers by using a linearly scanning all-fiber probe. (b) The B-scan raw data as well as a typical A-line signal. (c) The reconstructed image. (d) The enlarged image of a selected phantom fiber. (e) Point spread curves along the lateral and axial (red and blue dashed lines) directions with the envelope of the axial curve.

Fig. 4. Ex vivo ultrasound imaging of a section of the swine trachea. (a) A photograph of the sample with a 1 mm scaled ruler below. (b) The 2D image. Pixel numbers: 1200×400. OW: outer wall; IW: inner wall. (c) A snapshot of a 3D volumetric image. Voxel numbers: 1800×250×640. Dimensions of the spatial extent (labeled by the white box): 4.5mm×2.5mm×4.3mm.