Fabrication of broadband absorbing coatings for amplified spontaneous emission suppression

Amplified spontaneous emission (ASE) is a critical factor that limits the output power of slab lasers. To suppress the ASE effect in slab lasers, this paper proposes a metal/dielectric broadband absorbing coating between the laser gain medium and the metal heat sink to suppress ASE from zero to total internal reflection angle on the facet from inside the laser medium. Based on accurate characterization of Cr metal thin films, Cr/SiO₂ broadband absorbing films for 1064 nm YAG slab lasers are designed and fabricated to suppress ASE. The good agreement between experiment and design shows the reliability to suppress ASE in slab lasers.