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

Abstract

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.

High-speed photoacoustic microscopy: A review dedicated on light sources

“…Especially, wavelengths of ∼2 μm can be generated by the cross-relaxation process, which is one of the most efficient ways, using a 790 nm diode laser. Li et al applied a 1690–1750 nm tunable Tm 3+ -doped fiber laser with 10 kHz and 50 kHz PRR suitable for peak optical absorption of lipid (e.g., ∼1720 nm) to PAM, and PA images of adipose tissue were obtained [ 106 , 107 ].…”

All-Fiber Tunable Pulsed 1.7 μm Fiber Lasers Based on Stimulated Raman Scattering of Hydrogen Molecules in Hollow-Core Fibers

“…Normally, there are mainly two kinds of methods to generate 1.7 μm band laser emission. One is to pump rare-earth-doped fibers, including thulium-doped fibers (TDFs) [ 5 , 6 ], bismuth-doped fibers (BDFs) [ 7 , 8 ], and thulium–holmium co-doped fibers (THDFs) [ 9 , 10 ]. However, the conversion efficiency of TDFs is relatively low due to strong reabsorption in the 1.7 μm band, while the preparation technology of BDFs and THDFs are not mature.…”

Application of Hollow-Core Photonic Crystal Fibers in Gas Raman Lasers Operating at 1.7 μm

“…However, reported works mainly involve 1.7 µm continuous-wave (CW) fiber lasers [1,2], and the pulsed fiber lasers operating in this wavelength region have not been researched fully, though they have unique advantages in some applications. For example, in bioimaging applications such as multiphoton microscopy [3,4], optical coherence tomography [5], and spectroscopic photoacoustic (PA) imaging [6,7], 1.7 µm pulsed lasers can be used to realize three-dimensional (3D) volumetric imaging by time-resolved ultrasonic detection [7]. Similarly, in methane detection, the 3D distribution of the CH 4 concentration in space can be measured by using the time-of-flight ranging method to analyze the temporal characteristics of pulsed lasers when the pulsed lasers are in the 1.7 µm band used as the detection signal [8].…”

“…Similarly, in methane detection, the 3D distribution of the CH 4 concentration in space can be measured by using the time-of-flight ranging method to analyze the temporal characteristics of pulsed lasers when the pulsed lasers are in the 1.7 µm band used as the detection signal [8]. In fact, whether in bioimaging or gas detection, high-power 1.7 µm pulsed lasers are conducive to achieving higher sensitivity and deeper penetration/detection [7,9]. Thus, it is important and necessary to increase the output power of 1.7 µm pulsed fiber lasers.…”