A novel method for eliminating crosstalk in spectral beam combining of fiber lasers with an external cavity

• A novel crosstalk suppression method for SBC using cascaded reflective volume Bragg gratings. • Critical thresholds are identified: crosstalk eliminated when divergence <1.31 mrad, width <1.06 nm, temp <123.3°C. • The system design is validated experimentally under room-temperature and thermal conditions, confirming no crosstalk. • The method provides a cost-effective solution with 91% efficiency and thermal robustness. • Key design guidelines are offered by calculating essential R-VBG parameters for multi-wavelength SBC systems. Addressing the crosstalk issue in spectral beam combining (SBC) with an external cavity, a novel method to eliminate crosstalk by using cascaded reflective volume Bragg gratings (R-VBG) was proposed, and the required grating parameters, as well as threshold power in laser oscillation are calculated. The influences of beam divergence, spectral width, and thermal deformation of R-VBG for eliminating crosstalk were analyzed according to the calculated parameters. The simulation results show that, when the divergence angle, the spectral width, and the grating temperature are less than 1.31 mrad, 1.06 nm, and 123.3 ℃, respectively, the crosstalk between different emitters can be eliminated. On the basis of the designed system, an SBC experimental system using an R-VBG as combiner was established. The experimental results show that any one of the measured spectra for the combined beam is completely consistent with the spectrum of the corresponding single laser. Further, when the grating undergoes thermal deformation, the measured spectra of the combined beam are also consistent with the spectra of the measured beam at room temperature. The experiments under room temperature and grating thermal deformation indicate that the designed system can effectively eliminate the crosstalk.