Generation of Hermite-Gaussian modes in fiber-coupled laser-diode end-pumped lasers

A general model has been developed for the generation of Hermite-Gaussian modes in fiber-coupled laser-diode end-pumped lasers by off-axis pumping. Hermite-Gaussian modes can be used as an M ² standard in the calibration process due to the fact that these modes have a definite M ² factor. The present model predicts how the oscillation of Hermite-Gaussian modes is affected by the pump position, the pump size, and cavity mode size. A straightforward procedure have also been provided to design the optical coupling system for the lowest threshold in the generation of Hermite-Gaussian modes. All of the key parameters of the optimum pump condition are in terms of laser-diode beam quality and properties of the active medium. Experimental results have shown a fairly good agreement with the theoretical predictions.