Some Effects of Nonuniform Pumping on the Mode Structure of Solid State Lasers

The effects of nonuniform pumping upon the structure of near-axial low-order transverse modes of a laser cavity are considered. For transverse variations of the pumping level, the mode profiles may be severely distorted. The primary cause of the distortion arises from the spatial variation of the anomalous dispersion term in the dielectric constant associated with the laser line. Modes on the high-frequency side of the line center are distorted in such a way as to increase their gain relative to modes lying on or below line center. The results show that mode profile distortions are significant for pumping level variations of a few percent.