Ultra-large mode field area single-mode all-solid anti-resonant fiber with open arc elements in the cladding

What we believe to be a novel ultra-large mode field area (MFA) single-mode all-solid anti-resonant fiber (ARF) is proposed. Different from the large mode area (LMA) all-solid ARF with double layers of rods in the cladding, the proposed fiber utilizes open arc elements in the second layer instead of circular rods to simultaneously achieve the ultra-large MFA and high single-mode performance. Especially, the outer diameter (OD) of the fiber can be efficiently decreased in comparison with other LMA fibers with the same MFA. Through the combination of enlarging core diameter and adjusting the distance of the two layers of anti-resonant elements to expand the MFA, an ultra-large MFA of 15647 µm² can be achieved at the wavelength of 1.064 µm, which is 2 times that of the largest MFA of the previously reported all-solid ARF. The ratio of the lowest loss of higher-order modes to the loss of the fundamental mode can reach up to 23797 and thus high single-mode performance can be simultaneously implemented. Moreover, the OD of the designed fiber is only 578 µm, which is almost a quarter of that of the previous rod-type photonic crystal fiber and the mainstream large-pitch fiber (approximately 1.5-2 mm). To the best of our knowledge, it is the smallest OD among the currently reported ultra-LMA fibers with an MFA greater than 10000 µm². In addition, the tolerance to the change of fiber parameters is also discussed, demonstrating that the proposed fiber has a wide parameter tolerance range. Numerical results show that the all-solid ARF will be a great candidate for the future development of ultra-large MFA fiber.