Multiphoton excitations and nonlinear optical properties of exciton states in GaAs/AlxGa1-xAs coupled quantum well structure have been theoretically investigated under the influence of a time-varying high-intensity terahertz (THz) laser field.Non-perturbative Floquet theory is employed to solve the time-dependent equation of motion for the laser-driven excitonic quantum well system.The response to the field parameters,such as intensity and frequency of the laser electric field on the state populations,can be used in various optical semiconductor device applications,such as photodetectors,sensors,all-optical switches,and terahertz emitters.