Scaling of energy characteristics of polycrystalline Fe$^{2+}$:ZnSe laser at room temperature

The lasing characteristics of lasers based on diffusiondoped Fe$^{2+}$:ZnSe polycrystalline samples excited at room temperature by an electric-discharge HF laser are studied. A sample doped from two sides (working surfaces) emitted laser radiation with the energy $E=253$ mJ with the slope efficiency $\eta_d=33$ % and the efficiency with respect to the absorbed energy $\eta_{abs}\approx28$ % in the case of an elliptical pump spot of size $a\times b=6.8\times7.5$ mm. It is found that the possibility of increasing the lasing energy of the samples of these types by increasing the pump spot area (at a constant pump energy density) is limited by the appearance of parasitic generation typical for disk lasers. The first results are reported on the laser based on a polycrystalline sample made by a technology that allows one to form a zero dopant concentration on the surface and a maximum concentration inside the sample (i.e., to create a sample with internal doping). The possibilities of increasing the Fe$^{2+}$:ZnSe laser energy at room temperature by using multilayer samples fabricated by this doping method are discussed.