The temporal evolution of divergence of the output of a copper-vapor laser (CVL) operating with a high-magnification (M = 26.5) unstable resonator is measured by using a one-dimensional imaging system together with a fast gated linear diode array detector. The CVL output is found to consist of several temporally resolved components, with each successive component having lower divergence. The final component of the output has essentially diffraction-limited divergence. The divergence behavior is modeled by using an unfolded resonator-equivalent lens guide, with geometric constraints on the propagation of spontaneous emission within the lens guide, and is found to match the experimentally determined behavior.
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