Two sorts of microchip laser materials, such as Nd:YVO4 and Er/Yb:Cr phosphate Kigre glass, are used to perform the experimental study of pump absorption saturation. A spatial- dependent rate equation model has been developed for the simulation, and hence the corresponding absorption saturation intensities are determined, the pump saturation intensity is 840 W/cm2 in the (pi) -polarization, and 2200 W/cm2 in the (sigma) -polarization for the 3% a-cut Nd:YVO4 crystal for the 810 nm pump wavelength, and 130 kW/cm2 for Er/Yb:Cr phosphate Kigre glass for the 975 nm pump wavelength. Based on this nonlinear absorption effect, a high performance LD end-pumped Nd:YVO4 microchip laser was obtained with a low pump threshold of 3 mW and a high slope efficiency of 50%, while for Er/Yb:Cr phosphate Kigre glass laser, a low pump threshold of 5 mW and 20% slope efficiency was obtained when pumped by a Ti:Sapphire laser. All the laser operated in a single transverse mode, and the 1.535 micrometers laser operated at a single longitudinal mode. This study gives a useful guideline to design and to optimize the pump beam radius of LD end-pumped microchip lasers.