Emission spectrum and limits of quasi-cw operation of a neodymium laser with an intracavity plasma formed from a carbon target

A study was made of millisecond quasi-cw operation of a high-power neodymium laser in which a feedback loop was established by reflection from a carbon target. This target reduced the width of the emission spectrum by a factor of about 10³ during an output pulse, compared with the spectrum obtained under normal free-running spiking conditions. Determination of the limits of quasi-cw operation showed that the threshold of nonlinear reflection of radiation from an erosion carbon plasma, expressed in terms of the density of the laser radiation power reaching the target, was I ≈ 100 MW/cm².