We have developed a highly sensitive two-dimensional (2D) polarimeter that can sensitively measure the direction of the principal birefringence axis as well as the phase shift δ with its sign when δ≪π/4. The principle of polarimeter, system hardware, processing software, and calculated power loss will be described. The power loss due to thermal birefringence was evaluated quantitatively using the Jones matrix method. This polarimeter was successfully used to measure the 2D birefringence distribution in the laser-diode (LD) pumped solid-state laser material. The 2D thermal- and mechanical-stress-induced birefringence distributions were measured using the proposed polarimeter and compared to a calculated one with good agreement in a LD-pumped rod. The measured relative phase shifts induced by thermal effects and the simulation obtained by a three-dimensional analysis code of thermal birefringence in a LD pumped solid-state laser slab also were quantitatively in good agreement. We found that the developed polarimeter will be useful for developing high power and high beam quality LD pumped solid-state lasers. © 2001 American Institute of Physics.