Yb3+-doped rod-type amplifiers with local adiabatic tapers for peak power scaling and beam quality improvement
in: Laser Physics (2017)
The use of short local tapers in large mode area fiber amplifiers is proposed for peak power scaling while maintaining good beam quality. To avoid modal distortions, the powder-sintering (REPUSIL) method was employed to obtain core materials with excellent refractive index homogeneity. First experiments with Yb3+-doped rod-type amplifiers delivered 2ns pulses with peak powers of 540kW and energies of 1.4mJ for the untapered rod and 230kW for the tapered rod (limited by facet damage). The beam quality improved from an M2 value of approximately 10 to 3.5. The investigation of the taper structure indicates room for further improvement.