Frequency dependence of the amplifying parameters of a CuBr laser

A pair of copper bromide lasers in an oscillator–amplifier configuration was used to investigate the small-signal gain and saturation intensity as amplifying parameters in terms of pulse repetition frequency. Some fluctuations in the laser output power were recorded by varying the excitation frequency from 13 to 29 kHz as well as the amplifying parameters. The effect arises from the laser tube, which performs as both an optical resonator and an acoustic resonator. At some frequencies, which were matched by tube acoustic resonance, the acoustic energy overcomes the optical energy. The relation between frequencies that give maximum and minimum laser output powers was obtained so that the frequency that corresponds to a minimum laser output power is the average of two adjacent frequencies that correspond to a maximum output power. An empirical formula was obtained to calculate the optimum operational frequency in terms of tube diameter, which gives a maximum laser output power. The efficiency of the laser is highest at the lowest pulse repetition frequency, which gives considerable output power.