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 at 1700, 1725, and 1750 nm, three similar lasers are realized with a cavity length of around 25 cm. Under a maximum pump energy of 300 μJ at 1560 nm, laser pulse energies of 58.2, 66.8, and 75.3 μJ 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 18.8 μm and an axial resolution of 172.9 μm 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.

中文翻译：

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用于脂质体积光声成像的高能全光纤增益开关掺铥光纤激光器

我们展示了一种用于脂质体积光声 (PA) 成像的高能全光纤短波长增益开关掺铥光纤激光器。激光腔是通过在一对光纤布拉格光栅 (FBG) 之间嵌入一小段增益光纤来构建的。通过使用三对工作波长分别为 1700、1725 和 1750 nm 的 FBG，实现了三个相似的激光器，腔长约为 25 cm。在 1560 nm 处的最大泵浦能量为 300 μJ 下，激光脉冲能量分别为 58.2、66.8 和 75.3 μJ，最小脉冲宽度 <16.7 ns，重复频率为 10 kHz。通过使用与新开发的源结合的 PA 显微镜系统扫描脂肪牛肉切片来验证脂质的体积成像，横向分辨率为 18.8 μm，轴向分辨率为 172。达到 9 μm。此外，开发源的更高拍摄速度可能允许以两倍于当前血管内 PA 成像的帧速率增加。