Mid-infrared seven-core chalcogenide fiber with ultra-large mode field area and high beam quality

Abstract

A seven-core chalcogenide fiber with an ultra-large mode field for mid-infrared range of 2.5-11 μm is designed and fabricated. Through manipulation of the core radius and pitch in the seven-core configuration, we are engaged in a comprehensive exploration of crosstalk characteristics and the mode field area (MFA). In addition, the relationship between the parameters of seven-core fiber for infrared and the beam quality of the output laser is analyzed for the first time. A theoretical MFA of 8914 μm2 can be calculated with a core radius of 24 μm and the pitch of 50 μm. This impressive MFA is realized through the deployment of an improved drilling technique in the fabrication of a Ge-As-Se seven-core fiber. The fiber has a relatively low loss at the wavelength range of 2.5-11 μm, and the minimum loss is 1.4 dB/m at 8.5 μm. The measured MFA of the fiber at 10.6 μm is 7364 μm2, which is 6.2 times higher than that of traditional stepped single-core fiber, but slightly lower than the theoretical value. The power delivery capability of the fiber has been significantly improved about 2 times compared with that of single-core fiber. The output beam quality factor M2 is calculated as 1.13. In all, the seven-core fiber exhibits substantial potential for high-power laser propagation with high quality and flexibility.