Target loop adaptive optics: thermal blooming correction.

To evaluate adaptive optics (AO) concepts for the correction of nonlinear atmospheric phenomena occurring in high energy laser beam propagation and to perform AO system trade offs, a simple, but reasonably accurate, model of the entire AO loop is required. Heretofore, no such model existed which takes into account the temporal response of the atmosphere and yet is simple enough to permit extensive system tradeoffs. We have developed such a model. Optimum thermal blooming correction dictates that the atmospheric response time must be accounted for properly, especially for strong blooming strength. Experimental verification of the above model was carried out using an argon-ion laser with an iodine blooming cell and a closed AO loop to provide corrections for tilt, focus, and astigmatism. Reasonable agreement between theory and experimental data was achieved.