Two-photon absorption

Two-photon absorption is a process where a material absorbs two photons simultaneously, with their combined energy exciting an electron to a higher energy state. Unlike regular absorption, which involves one photon at a specific energy, two-photon absorption requires two photons of lower energy working together at the same time. This phenomenon is useful in advanced imaging techniques and microscopy because it allows precise targeting within tissues, reducing damage and increasing resolution. Essentially, two photons cooperate to deliver enough energy to activate the material, enabling sophisticated applications in science and technology.