Abstract
Hollow-core fibers provide an ideal environment for the interaction of a laser and gases; however, achieving stable and efficient coupling of a high-power laser is one of the key problems to be solved. Here, we study stable and efficient coupling of a high-power continuous-wave fiber laser with anti-resonant hollow-core fibers spliced with end caps. By optimizing the splicing process, a maximum laser power of 460 W was injected and 356.5 W was outputted under uncooled conditions, realizing a total transmission efficiency of approximately 77.5%. A test of more than 1 h showed the stability of this a coupling method. A few other important characteristics, such as the Fresnel reflection of the end caps and the influence of the end caps on the transmission beam quality, were measured and examined. This study opens new opportunities for stable and highly efficient coupling of high-power lasers with hollow-core fibers, which is significant for their applications in many other fields besides high-power fiber gas lasers, such as high-power laser delivery and liquid lasers in hollow-core fibers.
Highlights
Hollow-core fibers (HCFs) have generated significant attention because of their high damage threshold, low nonlinearity, and ideal environment for the interaction of a laser and gases [1]
One main cause is that the coupling of the pump with the core of an HCF that is sealed by gas cells has an almost free space structure, and the rubber plugs used in the gas cells for sealing are deformed at high power
The splicing between the HCF and the end cap is different from the splicing between the solid-core fiber and the end cap; because there is an interface between the silica and the air, a Fresnel reflection exists
Summary
Hollow-core fibers (HCFs) have generated significant attention because of their high damage threshold, low nonlinearity, and ideal environment for the interaction of a laser and gases [1]. One main cause is that the coupling of the pump with the core of an HCF that is sealed by gas cells has an almost free space structure, and the rubber plugs used in the gas cells for sealing are deformed at high power This influences both the coupling efficiency and stability. In 2005, an all-fiber gas cavity based on gas-filled hollow-core PCFs was reported, and the loss of splicing was approximately 1–2 dB, which was mainly due to the refractive index and mode field mismatch [18]. Three electrodes are used to heat the end cap to a molten state evenly, and subsequently, the electrodes shifted away by a short distance, and the waste heat is used to splice the HCF and the end cap
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