Beam Quality Deterioration in Dense Wavelength Beam-Combined Broad-Area Diode Lasers

We study various effects of beam quality deterioration in dense wavelength beam-combined direct diode laser systems based on broad-area laser diode bars of different filling factors. We mainly concentrate our research on external cavity architectures, where a transmission grating is used for simultaneous spectral stabilization and beam combining the emitters of a single laser diode bar. In this context, the residual spectral linewidth of the stabilized diode emitters, diode bar smile and spectral emitter crosstalk are the most relevant parameters which influence the resulting beam quality. On the basis of our results, we can deduce a lower limit for the beam quality of dense wavelength beam-combined broad-area diode lasers.