Multiphoton absorption and optical limiting

Optical limiting requires the development of materials exhibiting strong nonlinear absorption. Multiphoton absorption in materials can take the form of instantaneous two-photon absorption or time-integrating excited state absorption. We examine both types of mechanisms for optical limiting. Several experimental methods are used to study these phenomena and characterize materials. Often new or unusual effects arise in these experiments that require careful analysis to elucidate desired parameters. We describe several of these and give results for different materials relevant to optical limiting.