Laser active medium and process of manufacturing the same

A solid-state laser active medium comprising an optical gain material; a heat sink, wherein the heat sink is transparent, in particular over a wavelength range of 200 nm to 4000 nm, preferably with an absorption coefficient of <1 cm−1; the heat sink having a high thermal conductivity, in particular ≥149 W/(m*K); wherein the optical gain material and the heat sink exhibit a root-mean square, RMS, surface roughness of <1 nm; wherein the optical gain material is attached to the transparent heat sink by direct bonding.