有机高聚物PPQ薄膜的反常群速色散

Anomalous Group Velocity Dispersion of PPQ Organic Conjugated Polymeric Cast Film

通过对ＰＰＱ薄膜的吸收光谱的计算分析，由Ｋｒａｍｅｒｓ－Ｋｒｏｎｉｇ关系得出ＰＰＱ膜在５５０ｎｍ～７００ｎｍ左右波段存在负群速色散区，并且色散量相对较小，｜β２｜＜１．２ｐｓ２／ｍ。这使得对飞秒激光脉冲在ＰＰＱ平面光波导中传输的描述可以忽略色散项。根据这一简化，仅考虑自相位调制（ＳＰＭ）效应，由飞秒对撞锁模激光脉冲的光谱展宽所计算出ＰＰＱ的非线性折射率系数ｎ２，与报道的结果吻合得很好。

Integration calculations for the absorption spectrum of PPQ polymeric cast film, by means of the Kramers Kronig relation, were performed for a serial number of wavelengths. An existence of an region of anomalous group velocity dispersion (GVD) span near (550￣700) nm band was evidently indicated. The dispersion parameter β 2 is relatively small, |β 2|<1.2 ps 2/m, so that a dispersion neglected nonlinear Schordinger equation was used to described the propagating behavior of femtosecond colliding pulse mode locking (CPM) laser pulses in planar optical waveguide of PPQ film, and consequently, the obtained nonlinear refractive index coefficient n 2 was in a good agreement with the reported value.