In recent years, laser has made great progress in the field of biomedicine, especially in the field of minimally invasive surgery, because of its excellent monochromatism, collinearity and high energy density. Laser action on biological tissues, mainly using laser biothermal effect, and different wavelength and energy laser action on biological tissues produced thermal effect is not the same.

   Water molecules are the main components of biological tissues, and their absorption coefficients for different wavelengths of laser are important factors affecting the biothermal effect of laser. The absorption coefficient of water molecules to laser is as high as 600 cm−1 in the 2μm band, which is 6 orders of magnitude higher than that in the visible band. Therefore, thulium-doped laser can achieve shallow penetration depth of biological tissues and good thermal sealing effect.

   In the biomedical field, thulium-doped laser has been widely used. Thulium-doped laser can be used as an alternative to conventional tissue suture in stone lithotomy, varicose vein closure, minimally invasive laryngeal surgery, and oral squamous cell carcinoma resection, etc.

Applications of thulium-doped fiber laser:

   a.Tissue ablation

   b. Gravel

At present, the "gold standard" of clinical lithotripsy surgery is still holmium doped laser lithotripsy, but with its excellent lithotripsy effect, more and more researchers begin to regard thulium-doped laser as a new generation of laser lithotripsy. Future research directions for thulium-doped laser crushed stone mainly include: Higher frequency under the stone "crush" result in smaller and smaller optical fiber wound, design a higher radiation efficiency of optical fiber endings and laser parameters were optimized to achieve shorter repel the distance and the surrounding tissue, it needs more surgery in vitro rubble and clinical trials to further verify the feasibility of thulium doped laser lithotripsy and security.

   At the same time, in addition to tissue ablation and lithotomy, it is also an important direction for researchers to use the characteristics of water molecules with high absorption of thulium-doped laser to unlock more biomedical applications, such as laser-induced liquid microjet effect.

   The main problem in the development of thulium-doped fiber laser is that the pumping efficiency of active thulium-doped fiber is not high.And compared with 1 μm and 1.5 μm laser, 2 μm laser transmission loss, high environmental sensitivity, complex process, and related devices are customized, so the price is higher.Beside that,Active fiber and passive fusion splicing technology need to be improved.The control of fusion splicing loss between devices is also a challenge.

   Shinho S-12PM series fiber optic fusion splicer is applied to ultrafast fiber laser for medical use.It could support fusion splicing of active and passive optical fibers. the extinction ratio loss and splicing loss is very low.It has been highly appraised by users.

   Shinho fiber communication will keep paying attention to the development of thulium-doped lasers in medical treatment.