Numerical and experimental analysis of the influence of fiber power combiner on supercontinuum laser beam quality

We numerically calculated and analyzed the influence of a 7 × 1 fiber power combiner on supercontinuum (SC) laser beam quality in the range of 0.5 to 2.3 μm. The calculation results show the M2 oscillates within a range for a specific wavelength as the length of the output fiber changes. When the length of the output fiber is fixed, whether single input fiber or all fibers are injected with SC lasers, the M2 of the SC shows a nonlinear change and oscillates continuously throughout the entire spectrum, while it first decreases and then increases as the wavelength increases as a whole. Analysis of the numerical results shows that by changing the type of input fiber and the taper waist structure, the beam quality of both long-band and short-band parts of the SC laser can be improved. To verify theoretical calculations, the divergence angle of SC was measured as the beam quality after being transmitted by one 7 × 1 fiber power combiner in the spectral range from 0.5 to 2.3 μm. The divergence angle first decreases but then increases with a prolonging wavelength, and the curve of the experimental result renders a basic match with the calculation. To the best of our knowledge, currently no overall evaluation is reported on the beam quality of combined SC sources.