This technique is based on the two-photon absorption of dyes and the extended tunability of Ti:Sa lasers, thus allowing the use of various dyes with distinct absorption spectra and chemical ...

This causes an absorption spectra, as shown below. Because the energy levels are the same, the lines in the emission spectra of an element are in the same position as the lines in the absorption ...

This means that each electron transition will produce a photon of a different frequency and hence a different colour. This causes line emission spectra to be produced, as shown below. This is not ...

Photon upconversion involves a series of non-linear optical processes where the sequential absorption of two or more photons leads to the emission of a single photon with energy greater than the sum ...