Observation Of Three-Photon Enhanced Four-Photon Absorption
We report the measurement of instantaneous resonant four-photon absorption in the polydiacetylene-PTS [polymer poly(bis para-toluene sulfonate) of 2,4-hexadyine-1,6 diol]. Although normally too weak to be observable, an exact degeneracy between three- and four-photon absorption into the dominant exciton and two-photon states, respectively, resonantly enhances this effect so that it can be measured (four-photon coefficient [Formula presented]) at its peak wavelength of 1900 nm. Femtosecond measurements from 1200 to 2200 nm of two- and three-photon absorption, and the nonlinear refractive index coefficient are also reported. © 2003 The American Physical Society.
Physical Review Letters
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Yoshino, Fumiyo; Polyakov, Sergey; and Liu, Mingguo, "Observation Of Three-Photon Enhanced Four-Photon Absorption" (2003). Scopus Export 2000s. 1647.