External cavity design of high-power diode laser for polarized helium-3 neutron spin filters based on spin-exchange optical pumping

► The optics in the external cavity of a high-power laser diode for SEOP were investigated by ray tracing. ► The ray-trace calculations demonstrated that a doublet lens in front of the laser eliminates aberrations. ► The maximum spectral peak height in the doublet optics was found to be 25% higher than for a singlet lens.