Research on near-infrared ultrafast excited carrier dynamics of a pyrene-based derivative and its application in femtosecond laser

Abstract

Femtosecond laser, compared to continuous wave (c.w.) or nanosecond laser, has shown great promise in diversities of frontier applications because of its extremely short pulse width, high peak power and low thermal effect. In order to obtain femtosecond laser output, the design of suitable saturable absorber (SA) materials as a nonlinear modulation device is a key issue for a given laser system. However, the previous SA materials are limited in inorganic semiconductors, which have some constraints such as narrow working wavelength ranges, complex preparation process and high cost. By contrast, organic semiconductors have high molecular design freedom, good flexibility, simple preparation process, and low cost, and would act as an ideal SA material. Here, we report a novel strategy to tune and realize the femtosecond laser out by employing an organic small molecule SA of (Z)-2-(4-(pyrene-1-yl) phenyl)-3-(4-(1,2,2-triphenylvinyl) phenyl) acrylonitrile (Py-TPE). We show that Py-TPE has an ultrafast excited carrier relaxation time less than 20 ps, shorter than most of inorganic semiconductor materials. More importantly, by depositing such Py-TPE on the surface of tapered fiber as an SA device in Er-doped fiber laser system, an ultrafast fiber laser output with a pulse width as narrow as 447 fs and good stability was realized. This is the first report, to the best of our knowledge, to achieve femtosecond laser by taking advantage of the Py-TPE with ultrafast excited carrier relaxation time. These results demonstrate that Py-TPE is a novel organic saturable absorption material with great potential application in ultrafast laser and photonics.