Research On The Key Technology Of High-power Low-numerical Aperture Cladding Optical Stripper

Fiber lasers are widely used in medical and health,industrial processing and military defense,because of their good beam quality,stable performance and compact structure.As the core device of the fiber laser,the cladding light stripper(CLS)plays the role of stripping the cladding light and optimizing the beam quality.In recent years,the output power of fiber lasers has been continuously improved,and the cladding light power in the system has also been increasing,which puts higher requirements on the parameters of the stripper.In this paper,we analyzed the stripping principle of chemically corroded stripper based on the light theory,and constructed a stripping model of the cladding light.The model is used to simulate the relationship between the cladding light attenuation and the corrosion length,the residual diameter of the cladding and the roughness.We build a stripper test system,and verify the simulation results.In order to increase the stripping power,we studied the thermal effect of the high power cladding strippers,improved the corrosion scheme,stripped the cladding light by multi-stage etching,and simulated the residual power and corrosion length of the cladding light and the overall temperature of the device under the corrosion condition.The experiment measured the relationship between the scattered return power and the temperature rise of the coating under multi-stage corrosion.The results show that segmental corrosion can effectively improve the uniformity of cladding light stripping,reduce the scattering return power,reduce the temperature rise coefficient of coating layer and heat sink,and solve the problem of local overheating in the corrosion section of fiber.In order to improve the stripping effect of the corrosion-type stripper on the low numerical aperture cladding light,based on the stripping model of the cladding light,we simulated the relationship between the residual power and the corrosion length of the different numerical aperture cladding light and built two test systems to perform strip test on double-clad fiber and coreless fiber.The results show that the corrosion-type stripper has better stripping effect on the cladding light with larger numerical aperture,and optimize the corrosion parameters,a large attenuation can also be achieved for low numerical aperture cladding light.Based on the previous research results,we have produced a high-power low-numerical aperture stripper with a stripping power of 1136 W and successfully applied to a 3.9kW fiber amplifier.