In telecommunication and sensing arenas, InP-based Photonic Integrated Circuits (PICs) have been found compelling improvements in cost and function as well as size, weight and power consumption. A serious thermal management challenge has been put forward to high-density PICs designs, particularly for laser arrays. Employing 3D heat conduction equation and finite element method (FEM), this paper presents laser-to-laser spacing is a factor affects temperature distributions across the sampled grating distributed Bragg reflector (SG-DBR) laser array. According to the power consumption of thermoelectric cooler (TEC), single-stage and two-stage TECs can be then used to ensure the laser array works properly under different ambient temperature situations. In conclusion, the laser-to-laser spacing of the array should be larger than 50 µm to ensure static temperature variation of each laser in array blow the tight temperature limits (±0.1 K) and the two-stage TEC is a better choice when laser array is at high temperatures (above 40 °C).