Frequency up-conversion of 800 nm femtosecond pulses by two-photon absorption in doped PMMA fibers

We report on frequency. up-conversion of 175 femtosecond pulses in an all-polymer doped fiber configuration by resonant two-photon absorption. The PMMA fibers were doped with a novel organic chromophore 1,4-bis(4-diphenylamino-styryl)-benzene (referred to as SP35) which is designed specifically to emit in the blue spectral region. Strong upconverted blue emission was observed in the fibers when longitudinally pumped at 800nm with a Titanium Sapphire laser. We measured a large two-photon absorption cross section for SP35 of 7.8 x 10(-19) cm(4)/GW using the non-linear transmission method. Our study shows that a well designed organic chromophore in combination with a suitable fiber geometry makes this system appealing for the development of an upconversion blue laser source.