Abstract. In a calculation of demonstrative type collective, laser-like behavior of low energy nuclear fusion reaction of deuterons in crystalline environment is investigated. It is found that the reported extra 4 He production can be appropriately described with a model well known in quantum electronics in which the quantized boson ( 4 He) field interacts with an ensemble of two-level systems in a crystal resonator. The estimated life times of the two levels indicate that population inversion may be achieved. Thresholds of the deuteron number of the sample and of the electric current density of the pumping electrolysis are estimated in the calculation by analyzing the gain parameter and some other characteristics of the process.