The effect of injected intensity on the spectrum of an HgBr oscillator

The injection-locked bandwidth of an HgBr laser has been measured as a function of the injection intensity. It is found that the locked bandwidth is always at least twice the master oscillator bandwidth of 0.025 nm and increases slightly with the injected intensity to a maximum of 0.075 nm when 8 kW/sq cm is injected. These effects, which have been observed for the first time, are thought to be the consequences of either multilevel systems with collisional mixing rates considerably slower than the simulated emission rates, or isotopes of HgBr2. These effects can be overcome to a certain extent by using isotopically pure HgBr2 or operating at high buffer gas pressures to increase collisional mixing.