Yoshino F, Polyakov S, Liu M, Stegeman G. Observation of three-photon enhanced four-photon absorption.
PHYSICAL REVIEW LETTERS 2003;
91:063902. [PMID:
12935074 DOI:
10.1103/physrevlett.91.063902]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2003] [Indexed: 05/24/2023]
Abstract
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 alpha(4)=0.01 cm(5)/GW(3)) 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.
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