The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators.

To achieve a 3.02 kW Yb-doped fiber laser oscillator, the behavior of transverse mode instability (TMI) is experimentally studied in different pumping configurations; co, hybrid, counter, and bidirectional. A comparative analysis showed that population inversion saturation has a substantial impact on TMI threshold enhancement in high power fiber oscillators.

Wavelength alteration measurement using the Moiré technique.

For convenient measurements in many applications, wavelength alterations should be translated to the change in intensity of the output light. In this Letter, a novel method based on monitoring the Moiré pattern using a simple dispersive planoconvex lens (chromatic aberration) for wavelength alteration measurement is reported. Due to the chromatic aberration of the lens, different wavelengths have different magnifications.