Study On Optical Limiting Characteristics Of Ionic Nonlinear Optical Organic Materials

Laser pulses generated by ultra-high-energy pulsed lasers might adversely affect the human body(such as eyes)and high-precision instruments.Optical limiting(OL)refers to the phenomenon that when the laser irradiates the optical limiting material,the transmittance decreases with the increase of the energy of the high-energy ultrafast incident pulsed laser.Therefore,materials with excellent optical limiting properties can be used in protecting the sensitive equipments and human eyes from damage caused by high-energy laser pulses.In this work(thesis),DAST and OHB-T,two typical ionic nonlinear optical organic materials,were systematically investigated.Accordingly,novel composite films that are composed of DAST or OHB-T and silver nanowires(AgNWs)have been successfully prepared.These composite films exhibit better comprehensive performance of optical limiting.The main contents of this work are divided into three parts shown as follows:(1)The OL characteristics of the nonlinear organic material DAST were investigated,and the composite films composed by DAST and polymer PMMA were prepared.Under the laser irradiation of 355 nm wavelength and the same laser radiation intensity,the normalized transmittance of the DAST-PMMA binary composite film compounded with DAST is lower than that of the pure PMMA film.Under the condition of 532 nm laser irradiation,obvious reverse saturable absorption(RSA)responses were observed.DAST-PMMA composite film shows excellent nonlinear absorption performance.The OL characteristics can be optimized in future works by adjusting the DAST concentration in the DAST-PMMA composite film.(2)The solution casting method is used to prepare all-organic OHB-T-PMMA composite films.Results reveal that under 532 nm laser irradiation,OHB-T-PMMA composite films show excellent non-linear absorption performance.And as the weight ratio of OHB-T increases(from 0.2 mg/m L to 0.8 mg/m L),the normalized transmittance gradually decreases and the nonlinear absorption coefficient ? increases.The measured nonlinear absorption coefficient ? of DAST-PMMA and OHB-T-PMMA composite films are 110.6 cm/GW and 101.6 cm/GW,respectively.Both materials show excellent nonlinear absorption performance.(3)Two ionic nonlinear optical organic materials DAST and OHB-T were further composed with AgNWs to prepare DAST-AgNWs-PMMA and OHBT-AgNWs-PMMA two new ternary composite films.Compared with the all-organic DAST-PMMA and OHB-T-PMMA composite films,the measured nonlinear absorption coefficient ? of DAST-AgNWs-PMMA and OHB-T-AgNWs-PMMA ternary composite films with AgNWs added are 136.5 cm/GW and 119.6 cm/GW,respectively.The normalized transmittance of these two ternary composite film is further reduced,and the nonlinear absorption coefficient ? increases,indicating the optical limiting of the latter is further improved.Based on this,this research has explored a new way to improve the optical limiting performance of materials,laying a foundation for exploring optical limiting materials and devices with practical application value.