Large-mode-area (LMA) fibers working with advanced mechanisms have been established as promising candidates for next-generation high-power fiber lasers, benefitting from their potentials in mode area scaling, higher nonlinear threshold, and feasibilities for some functional applications[1–6]. More recently, a kind of bandgap-guided microstructure fiber, called the all-solid photonic bandgap fiber (AS-PBGF), has become an emerging research focus[7–12]. Free of air-holes structures, AS-PBGF exhibits excellent practical convenience for the high-power platform and portability for the double-cladding design or polarization-maintaining scheme. The all-solid structure ensures the ease of cleaving and splicing, making a compact all-fiber configuration possible. Robust single-mode (SM) operation with high loss ratio between the fundamental mode (FM) and high-order modes (HOMs) is achievable due to the open-cladding of AS-PBGF. By combining the stack-and-draw method with rare-earth doping technology, the production of active AS-PBGF has gradually become an internal technology mastered by only a few organizations[8,9,11,12,14,15]. Over kilowatt-level emission by using double-cladding active AS-PBGF has been successfully demonstrated. Besides, the multi-resonant and hetero-structured designs further open a new path for the super LMA AS-PBGF design[8,17,18]. With all of the above advantages integrated, the controllable distribution of photonic bandgaps (PBGs) of AS-PBGF additionally provides a novel approach for selective wavelength filtering[13,19]. Therefore, AS-PBGF takes most of the prerequisites for high-power laser applications. Currently, the physics of AS-PBGF optical guidance is a fascinating and ongoing topic of research.