A research team from Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS) reported the design, fabrication, and characterization of a passive silicate-glass-based all-solid anti-resonant fiber (AS-ARF) for ∼1 µm transmission suppression. The results were published in Optics Express on September 5, 2024.

　　Currently, anti-resonant hollow-core fibers are widely studied due to their advantages of large mode field single-mode transmission and filtering properties. However, industrial applications still face certain limitations due to the high complexity of fabrication and splicing. Therefore, developing a large mode field fiber with an all-solid anti-resonant structure is expected to expand its applications in high-power active and passive fiber lasers.

　　In this work, the simulation results of the research team show that the AS-ARF (Anti-Resonant Fiber) can achieve a higher-order mode (HOM) suppression ratio of over 25 dB at a wavelength of 1550 nm and a core diameter ranging from 26 to 63 μm. A silicate-based passive AS-ARF was fabricated using a combination of hole-assisted and jacketed high-temperature drawing techniques. As shown in Figure 1(a), the core diameter is 43 μm, the numerical aperture is 0.023, and the high-refractive-index ring wall thickness is 1.4 μm. The results in Figure 1(b) and (d) confirm that it has large mode field single-mode transmission and filtering properties. By splicing a 12 cm-long AS-ARF in an EYDF amplifier, the amplified spontaneous emission of Yb³⁺ ions was effectively suppressed, and the loss at the 1030 nm band was 12.3 dB higher than that at the 1550 nm band. To our knowledge, this is the first demonstration of ~1.5 μm single-mode propagation and ~1 μm transmission suppression in an AS-ARF. This novel fiber structure is expected to be further applied in rare-earth-doped fiber amplifiers and lasers, including those doped with Nd, Yb, Er, Tm, and other rare-earth elements.

　　This research was supported by the Strategic Priority Research Program of the Chinese Academy of Science; Key Programs of the Chinese Academy of Sciences; Key R&D Program of Shandong Province.

　　Fig. 1 (a) Cross-sectional view of the AS-ARF; (b) The black curve represents the transmission spectrum of a 40 cm-long AS-ARF in the wavelength range of 0.5-1.7 μm, and the red curve shows the calculated fundamental mode loss; (c) and (d) depict the variation of the output beam profile under different coupling conditions.

　　Article website: https://doi.org/10.1364/OE.527717