Small-signal step response of laser amplifiers and measurement of CO2laser linewidth

As part of a general program of research on time response of a laser medium to optical transients, we have studied the linear (small-signal) response to a rectangular pulse signal input, both theoretically and experimentally. The theory for the case of Lorentzian homogeneously and Gaussian inhomogeneously broadened transitions has been developed using a two-level density matrix formulation. The results are negligibly different for the two broadening mechanisms for an amplifying medium, where the line center contribution is most important. The step response of a laser is measured experimentally and the bandwidth of the medium is deduced. Its pressure dependence in a mixture of CO2, N2, H6of 1:0.88:4.53 is determined.