The electro-optic and nonlinear optical properties of self-organized InxGa1-xAs/GaAs quantum dots were studied experimentally. The quantum dot heterostructures were grown by molecular beam epitaxy. The measured linear and quadratic electro-optic coefficients for In0.4Ga0.6As quantum dots are 2.58×10-11 m/V and 6.25×10-17 m2/V2, respectively. For InAs quantum dots, the measured linear and quadratic electro-optic coefficients are 2.43×10-10 m/V and 3.37×10-17 m2/V2, respectively. Pump–probe differential transmission spectroscopy measurements were made on the dot samples at cryogenic temperatures with linear and circularly polarized pump and probe beams. The ground and excited state recombination times are 620 and 290 ps, respectively. © 2001 American Vacuum Society.