Study On Nonlinear Optical Properties Based On Poly(3-hexylthiophene) Materials

With the development of information technology,people's requirements for network information capacity and computer speed are increasing,and thus the nonlinear optical materials that play a decisive role in the realization of all-optical networks have attracted extensive attention in the research field.In this paper,the nonlinear optical properties of the conductive polymer poly(3-hexylthiophene)(P3HT)are studied.The nonlinear optical properties of P3 HT were investigated by nonlinear open-aperture Z-scan test,and it was further found that P3 HT solution and film exhibited different nonlinear optical characteristics.Furthermore,the excitation and relaxation processes of P3 HT molecules were explored by pumping,and the P3 HT films and solutions exhibited different nonlinear optical behaviors from the aspect of molecular ultrafast kinetics.On this basis,graphene carbon nanomaterials were combined with P3 HT by physical mixing and chemical bonding to study the effect of graphene carbon nanomaterials on the nonlinear optical properties of P3 HT.The main structure of the paper is as follows:The first part focuses on the nonlinear optical properties of P3 HT solution.The study found that at 532 nm,the nonlinear absorption of P3 HT solution samples showed different phenomena under picosecond and nanosecond lasers: the nonlinear open-cell Z-scan of P3 HT solution samples showed reverse saturation absorption under nanosecond laser.It exhibits saturated absorption under a picosecond laser.In addition,as the picosecond laser energy increases,the nonlinear absorption of the P3 HT solution sample changes from saturated absorption to reverse saturation absorption.Aiming at this transformation phenomenon,the paper further explores the causes of the above phenomena through pump detection and transient fluorescence decay life experiments,and proposes a four-level model of excitedstate two-photon absorption under single photon induction in P3 HT solution state.The second part studies the nonlinear optical properties of the P3 HT film.At 532 nm,the results of non-linear open-cell Z-scan test on P3 HT films and solutions show that under nanosecond pulsed laser,P3 HT film exhibits nonlinear saturated absorption,while P3 HT solution exhibits nonlinear reverse saturation absorption.Both samples exhibited nonlinear saturated absorption under picosecond pulsed laser.Through further investigation of pump detection experiments,it was found that P3 HT in film and solution state is two different excitation and relaxation processes: compared with the relaxation process of P3 HT solution,there is a sudden increase in transmittance during the recovery of P3 HT film.The point divides the relaxation process into two parts.Furthermore,the transient fluorescence decay lifetime of P3 HT film was tested and fitted by e-index.The results show that it satisfies the double exponential fitting and the decay process corresponds to two times;while the transient fluorescence decay of P3 HT solution satisfies the single exponential fitting and corresponds to only A response time is returned,which is consistent with the results of the pump detection experiment.Aiming at the difference between the properties of the film and the solution sample,a mixed solvent of CHCl3 and absolute ethanol was prepared.By changing the volume ratio of anhydrous ethanol to simulate the transformation process of P3 HT solution to the film state,the performance change of P3 HT under different precipitation levels was studied.The results of UV-visible absorption,fluorescence and Z-scan showed that P3 HT molecular chain spacing,molecular force and alignment mode have significant effects on the nonlinear optical properties of P3 HT.The third part is mainly on the premise of the detailed understanding of the nonlinear optical properties of P3 HT,and focuses on the influence of graphene(GR)carbon nanomaterials on the nonlinear optical properties of P3 HT.The complexes of GR and P3 HT were physically blended and chemically grafted to obtain GR-P3 HT and GO@P3HT,respectively.The results of nonlinear open-aperture Z-scan test show that GR can significantly change the nonlinear optical properties of P3 HT.Mainly reflected in the following aspects: compared to the transient fluorescence decay life curve of P3 HT solution samples,the transient fluorescence decay lifetime of the complex GO@P3HT obtained by grafted is shorter than that of P3 HT solution.The GO@P3HT and P3 HT solutions showed saturated absorption in the picosecond Z-scan test results.In the pump detection result,the transmittance of the composite product GO@P3HT in the negative retardation phase is greater than the normalized transmittance,which is opposite to the transmittance in the negative retardation phase of the P3 HT solution sample.