Four-Photon Process Induced Upconversion Lasing

摘要: It is measured that upconversion fluorescent intensity of a new molecule proportional to the quartic excitation density. This demonstrates it four-photon absorption process. Furthermore, at high-density ultrashort pulse laser pumping, an emission appears satisfy four criteria lasing, including highly directional emission, short duration, spectral narrowing, and changing linear output/input relationship above threshold. The experimental results demonstrate four-photon-process-induced amplified spontaneous occurs.