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Nonlinear Optical Properties Study Of Porphyrins And Squaraine Molecules Based On Femtosecond Z-Scan Technology

Posted on:2024-07-19Degree:MasterType:Thesis
Country:ChinaCandidate:L Y SongFull Text:PDF
GTID:2531306917999329Subject:Chemistry
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Nonlinear optical materials have good prospects in the fields of photodynamic therapy,optical limiting,and laser modulation,which have attracted widespread attention from scientists,and it is especially important to find nonlinear optical materials with excellent performance.In this thesis,we focus on two organic conjugated materials,porphyrins and squaraine,both of which have large π-conjugated structures and high chemical and photothermal stability,and have great potential for application in the field of optical nonlinearity.With the development of laser technology,Z-scan technique has become an important tool to characterize the nonlinear properties of materials due to its simple device and high sensitivity.In this thesis,the nonlinear optical properties of two new self-assembled porphyrin molecules(P1 and P2)and squaraine molecule(new Donor-Acceptor-Donor(D-A-D)structured composite films SQ1@PMMA and SQ2@PMMA)were investigated in the near-infrared wavelength range using a modified single-beam femtosecond Z-scan test system,and important optical parameters were obtained to explore their potential as two-photon photodynamic therapy,optical limiting and near-infrared laser materials.limiting,and near-infrared laser materials.The research of this thesis includes:1.A multi-wavelength single-beam femtosecond Z-scanning device is built.Using Galileo telescope system,the spot quality is improved,the accuracy and reliability of measurement are improved,and the nonlinear test of solid,liquid and uniform thin film can be completed.An I-scan testing system is built independently,which improves the accuracy of thin film sample testing and can be used for the measurement of non-uniform thin film samples.2.Based on the self-built femtosecond Z-scan device,the third-order nonlinear optical properties of self-assembled porphyrins P1 and P2 were studied,and their application potential in two-photon photodynamic therapy(two-photon photodynamic therapy,2PA-PDT)was evaluated.Both of them are photosensitizers with good water solubility.in aqueous solution,P1 exists in the form of monomer and P2 exists in the form of aggregates(two-dimensional nano-flakes).Z-scan results in the near-infrared wavelength range show that both of them are two-photon absorption(2PA),which verifies the possibility of their application in near-infrared 2PA-PDT.In addition,optical limiting experiments have been carried out,and the results show that it can be used for ultrafast response protection of continuous broadband lasers,expanding its application range.3.Squaricine composite films SQ1@PMMA and SQ2@PMMA were prepared for the first time.Their nonlinear absorption properties in the near infrared wavelength range of 700-900 nm were measured by femtosecond Z-scan device,and the corresponding nonlinear absorption coefficients were obtained by formula fitting.The Z-scan signal shows a W-type transition from reverse saturable absorption(reverse saturable absorption,RSA)to saturable absorption(saturable absorption,SA)at 700nm,while the signal at 800 nm and 900 nm is a single strong SA.The energy level model is established by using the theoretical calculation method of DFT/B3LYP,and a reasonable mechanism explanation is proposed.Finally,through the I-scan measurement,it is proved that it has ultra-high modulation depth and small saturated light intensity at 800 nm and 900 nm wavelengths,so it has great application potential in the field of near-infrared ultrafast laser.
Keywords/Search Tags:femtosecond Z-scan, self-assembled porphyrins, square acidocyanine composite film, two-photon photodynamic therapy, near-infrared laser
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