High power laser diodes have been widely utilized in many fields, like industry, scientific research, military and medical treatment, etc. However, thermal stress induced by packaging process due to CTE-mismatch between chip and heat-sink is the main source causing near-field non-linearity along laser bar (also known as "SMILE"), decreasing the degree of polarization (DoP), broadening spectrum, and degrading the lifetime of laser diode array (LDA). In this paper, the effect of packaging induced thermal stress on high power laser diode arrays was studied theoretically and experimentally. The FEM simulation and photoluminescence (PL) experimental results showed the difference of packaging induced thermal stress based on different packaging structures. Spectrally resolved spectrum of LDA showed the packaging induced stress is highest in the middle and rapidly drops near both ends of laser bar, in agreement with our theoretical simulation, resulting in spectral broadening due to blue shifting the lasing wavelength of the center emitter more than the edge emitters. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.