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Schematic of energy levels involved in two photons absorption. In atomic physics, two-photon absorption (TPA or 2PA), also called two-photon excitation or non-linear absorption, is the simultaneous absorption of two photons of identical or different frequencies in order to excite an atom or a molecule from one state (usually the ground state), via a virtual energy level, to a higher energy ...
Two-photon excitation employs two-photon absorption, a concept first described by Maria Goeppert Mayer (1906–1972) in her doctoral dissertation in 1931, [3] and first observed in 1961 in a CaF 2:Eu 2+ crystal using laser excitation by Wolfgang Kaiser. [4] Isaac Abella showed in 1962 in caesium vapor that two-photon excitation of single atoms ...
Here, pulsed laser sources, with pulse widths of around 100 fs, [1] are preferred as they deliver high-intensity pulses while depositing a relatively low average energy. To enable 3D structuring, the light source must be adequately adapted to the liquid photoresin in that single-photon absorption is highly suppressed.
In atomic physics, non-degenerate two-photon absorption (ND-TPA or ND-2PA) [1] or two-color two-photon excitation [2] is a type of two-photon absorption (TPA) where two photons with different energies are (almost) simultaneously absorbed by a molecule, promoting a molecular electronic transition from a lower energy state to a higher energy ...
High photon intensity experiments can involve multiphoton processes with the absorption of integer multiples of the photon energy. In experiments that involve a multiphoton resonance, the intermediate is often a low-lying Rydberg state, and the final state is often an ion. The initial state of the system, photon energy, angular momentum and ...
Laser light is a type of stimulated emission of radiation. Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level.
The first nonlinear optical effect to be predicted was two-photon absorption, by Maria Goeppert Mayer for her PhD in 1931, but it remained an unexplored theoretical curiosity until 1961 and the almost simultaneous observation of two-photon absorption at Bell Labs [4] and the discovery of second-harmonic generation by Peter Franken et al. at University of Michigan, both shortly after the ...
Two-photon photoionization is provoked by intense laser pulses of short duration. In this case, a first photon absorbed by DNA gives rise to an electronic excited state. During its lifetime, the latter may absorb a second photon.