High-energy all-fiber gain-switched thulium-doped fiber laser for volumetric photoacoustic imaging of lipids

We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic (PA) imaging of lipids.The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg gratings (FBGs).Through using three pairs of FBGs with operation wavelengths at1700,1725,and 1750 nm,three similar lasers are realized with a cavity length of around 25 cm.Under a maximum pump energy of 300μJ at 1560 nm,laser pulse energies of 58.2,66.8,and 75.3μJ are,respectively,achieved with a minimum pulse width of <16.7 ns at a repetition rate of 10 kHz.Volumetric imaging of lipids is validated through scanning a fat beef slice with a PA microscopy system incorporated with the newly developed source,and a lateral resolution of 18.8μm and an axial resolution of 172.9μm are achieved.Moreover,the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.