Digital Twin of a One‐Sun‐Driven Luminescent‐Concentrator‐Assisted Planar Solar‐Pumped Fiber Laser

Planar solar-pumped fiber lasers (SPFLs) based on luminescent solar concentrators (LSCs) enable direct conversion of one-sun irradiation into laser radiation. However, experimentally demonstrated performance remains limited, while the underlying mechanisms are insufficiently understood. In this work, a physics-based digital twin of LSC-assisted SPFL is developed using Monte Carlo ray tracing with explicit fiber geometry, coupled to rate-equation and power-propagation modeling. The model is validated against differential-gain and laser-output measurements. The analysis reveals that SPFL performance is constrained by weak photon–core interaction arising from the µm-scale core and low single-pass absorption probability in the Nd$^{3+}$-doped core. In the experimentally validated configuration, only 0.54% (0.34 W) of the incident power is absorbed within the core, corresponding to 35 mW laser output. Photon-flux analysis identifies 51.2% material-related losses and 48.3% cavity-related confinement losses associated with angular-dependent dichroic-mirror performance. Parameter studies demonstrate sensitivity of SPFL performance to sensitizer photoluminescence quantum yield, LSC refractive-index distribution, sensitizer thickness, and core diameter. Combining several improvement strategies within the present architecture yielded approximately 470 mW laser output and 0.67% solar-to-laser conversion efficiency representing 13-fold improvement relative to the baseline system (0.05%). The developed digital twin enables systematic investigation of alternative architectures and optimization of one-sun SPFLs.