Synthesis, characterization and third-order nonlinear optical behaviour of two novel ethyne-linked polymers

Two novel ethyne-linked polymers (P1 and P2) were synthesized and characterized. Via femtosecond Z-scan, their nonlinear optical properties were investigated. Both polymers exhibit obvious reverse saturable absorption and self-defocusing. Using phase object pump-probe method, their transient absorption and refraction dynamic traces are measured and the mechanism of their optical nonlinearities is analyzed. The results indicate that two photon absorption (TPA) mainly dominants nonlinear absorption of P1 and P2. The TPA coefficients are approximate 24.7 x 10(-2) cm/GW for P1 and 3.12 x 10(-2) cm/GW for P2. Through the extrapolation fitting, the estimated OL threshold for P1 is on the order of 10(-2) J/cm(2). On the other hand, both polymers display negative excited-sate refraction which is strong enough to dominate the transient nonlinear refraction over solvent effect. The refractive volumes of each effective state are determined. Our results indicate that ethyne-linked polymers have good nonlinear optical properties under femtosecond pulse excitation.

Automated summary

Two novel ethyne-linked polymers (P1 and P2) were synthesized and their nonlinear optical properties were investigated. The results showed that both polymers exhibit reverse saturable absorption and self-defocusing, with two photon absorption being the dominant nonlinear absorption mechanism. Additionally, the polymers also display negative excited-state refraction.