Large-mode-area multi-resonant all-solid photonic bandgap fiber with low bending loss and robust single-mode operation

•In this contribution, we have experimentally demonstrated a novel large-mode-area multi-resonant all-solid photonic bandgap fiber which is specifically optimized for conventional applications of fiber lasers around 1 μm, highlights in this work are listed as following literally.•A multi-resonant all-solid photonic bandgap fiber with a hexagon core exceeds 45 μm.•Transmission spectrum in the 3rd PBG exhibits a broad bandwidth from 970 nm to 1180 nm.•Bending loss lower than 0.1 dB/m of a 5-m-length fiber is obtained.•Robust single-mode operation of the fiber is verified with a negligible high-order-mode content less than −47 dB.•A preliminary conclusion about the relationship between beam quality and single-mode character is verified. In this paper, we have experimentally demonstrated a novel large-mode-area multi-resonant all-solid photonic bandgap fiber (AS-PBGF) which is specifically optimized for conventional applications of fiber lasers around 1 μm, with a hexagon core that is measured to be 46 μm in the corner-to-corner direction and a broad bandwidth from 970 nm to 1180 nm in the 3rd photonic bandgap (PBG). Bending loss lower than 0.1 dB/m of a 5-m-length fiber is obtained in the case of bending radius R greater than 25 cm. Robust single-mode (SM) operation of the fiber is verified within the whole PBG. In addition, we also report a phenomenon about the abnormal variation of M2 within the low loss region of the 3rd PBG. The evolution of beam quality within the 3rd PBG appears as a U-shaped curve rather than a constant. Finally, a preliminary conclusion about the relationship between the beam quality and SM characteristics in AS-PBGF which is quite different from that in conventional SIFs is verified.