Spectrally filtered all-solid photonic bandgap fiber for high-power and Raman-free laser delivery

Nonlinear effects hinder the ultimate performance of high-power laser delivery in solid-core optical fibers. Mitigating nonlinear effects through suppressing the unexpected gain is a promising strategy. In this work, we present a high-fidelity and Raman-free laser delivery employing the over 20-meter-length all-solid photonic bandgap fiber (AS-PBGF), which is designed for spectral filtering at the stimulated Raman band. The total transmission efficiency is 92.7% (total loss: 0.33 dB), and the maximum output power of 3004 W is delivered. Through optimizing the fiber matching and coiling states, the output beam quality of AS-PBGF only shows slight degradation (≤0.1) than the laser source, corresponding to the M² value of 1.52 at the highest power. No additional Raman emission is observed in the output spectrum.