ASE suppression in a thin-disk laser by optimizing reflectivity at an active element–heatsink interface

A method for suppressing the effect of amplified spontaneous emission (ASE) in a thin-disk (TD) laser is proposed. The method is based on reducing the reflectivity of the mirror surface of the active element at large angles of incidence and directing the ASE to the bulk of the heatsink. Reflectivity reduction is achieved through the optimization of the multilayer dielectric mirror and bonding active element and heatsink directly or with a high refractive index glue. The ASE effect and its impact on laser characteristics depending on the reflection coefficient profile at the mirror face are modeled. Active element (AE)-heatsink interfaces allowing nearly complete ASE suppression are proposed. This significantly increases the gain and stored energy, without affecting the signal and pump beams in any way.