Frequency-upconverted fluorescence and stimulated emission induced by multiphoton absorption (MPA) have attracted much interest. As compared with low-order MPA processes, the construction of high-order MPA processes is highly desirable and rather attractive, yet remains a formidable challenge due to its inherent low transition probability. We report the observation of the first experimental frequency-upconverted fluorescence and stimulated emission by simultaneous six-photon excitation in an organic molecular system. The well-designed organic conjugated system based on cross-shaped spiro-fused ladder-type oligo(p-phenylene)s (SpL−z, z=1–3) manifests reasonably high MPA cross-sections and brilliant luminescence emission simultaneously. The six-photon absorption cross-section of SpL-3 with an extended π-conjugation was evaluated as 8.67×10−169 cm12 s5 photon−5. Exceptionally efficient 2- to 6-photon excited stimulated emission was achieved under near-infrared laser excitation.
Scopus Subject Areas
- frequency-upconverted stimulated emission
- MPA cross-section
- multiphoton absorption (MPA)
- spiro-fused molecules