The small signal gain and the saturation intensity measurement of the nitrogen-ion laser

A series oscillator-amplifier has been fabricated and optimized in order to determine the small signal gain and the saturation intensity of the N₂⁺ amplifying medium. Two plasmas, which are composed of a mixture of helium and nitrogen gases, have been produced under pressures of 2–5 atm by applying an electrical transverse discharge. The time delay between the two plasmas has been controlled by the gas pressure. To optimize the gain, the entrance time of the oscillator's output pulse into the amplifier was synchronized with the maximum population inversion in the amplifier. The gain coefficient () was obtained from 6 to 124, by varying the intensity of the input beam at the optimum pressure. The small signal gain and the saturation intensity have been calculated as 0.04, 0.07, 0.10 cm⁻¹ and 7.77, 13.33, 19.97 (kW cm⁻²) at 1.25, 1.70, 2.20 atm, respectively. The dominant wavelength of the nitrogen-ion laser corresponding to the B²∑_u(v = 0) → X²∑_g(v′ = 1) transition, 427.8 (nm) wavelength, was used in this work.