Compensation of Laser Thermal Depolarization Using Free Space

Thermally induced birefringence in a single-transverse-mode laser for moderate pumping is well compensated when the rod is double-passed after reflection from a mirror one Rayleigh range away from the rod. The depolarized light is in a spatial (1, 1) mode and the relative Gouy phase shift between the fundamental and depolarized modes in propagating a Rayleigh range leads to good compensation.