| As a new technology, fiber optical communication has become the significant symbol of the new technological revolution and the main tool for all kinds of information in the future society. It has got rapid development and has found wide applications in recent years. The all-optical net (AON), which is based on DWDM, is also considered by many experts and scholars as the inevitable trend of the development of communication. All-optical switching (AOS), one of the key devices in the AON, is based on the nonlinear optical (NLO) principle to achieve a light control and has fast response time and high efficiency.NLO material has wide applications in many optical devices such as ultrafast AOS, laser Q-switching and high intensity optical storage. And it has attracted much attention these decades. NLO materials and their unique properties have sparked the imagination of chemists and physicists alike, as they make possible a wide range of processes and applications that will almost certainly be prerequisite to the realization of optical device applications, including the ultrafast AOS, laser passive Q-switching, high density optical storages and etc. In recent years, organometallic complexes have attracted much attention as a new type of NLO materials due to their large NLO susceptibility, architectural flexibility, and ease of fabrication. Our group selected dmit complexes as our research objectives.Firstly, by choosing Au and Ni as the central metalion, [(C2H5)4N]+,[(C3H7)4N]+ as ligand, four materials [(C2H5)4N][Ni(dmit)2], [(C3H7)4N][Ni(dmit)2], [(C2H5)4N] [Au(dmit)2] and [(C3H7)4N][Au(dmit)2], abbervad as EtNi, PrNi, EtAu and PrAu, respectively, are Synthesized. It is noted that these two Au(dmit)2 materials are reported for the first time.Secondly, the linear optical properties for the materials are studied using UV-Vis-NIR scanning spectrophotometer and prism coupler. And the third-order NLO properties are analyzed using Z-scan technique. Laser Z-scan technique has many advantages:simple experimental setup, high insensitivity and high resolution. Moreover, it can distinguish the real (nonlinear refractive index n2) and image part (nonlinear absorption coefficientβ). Therefore, we can choose the laser devices with different wavelengths and different pulse widths as the laser source of the Z-scan setup. Then the third-order NLO properties for the materials under different conditions with different laser wavelengths and different pulse widths could be obtained.Thirdly, the third-order nonlinear optical properties of the actoneitrile solution for these four materials are studied using Z-scan technique under the condition of 1064 nm, 20 ps laser,532 nm,14 ps laser and 1053 nm,18 ns laser, respectively. Furthermore, we devote to analyzing the factors which impact the third-order NLO properties of the materials. And several important conclusions have been obtained as follows:1. We study the influence of the molecular structure for the linear absorbtion spectrum and the third-order NLO properties. It is thought that central metal ion is the basic reason to decide the linear and NLO properties for dmit materials. Changes of the external cation can only make some adjustments on the strength of these properties; 2. The third-order NLO properties for the novel Au(dmit)2 complexes are studied under the condition of 532 nm and 1064 nm laser, respectively. The comparison is made from the linear absorption spectrum angle; 3. The third-order nonlinear absorption properties for the Ni(dmit)2 complexes are studied under the condition of 1064 nm,20 ps and 1053 nm,18 ns laser, respectively. It is proved that the laser width is an obvious factor to influence the third-order NLO properties and the property differences are discussed; 4. The third-order nonlinear susceptibility, nonlinear refractive index and nonlinear absorption coefficient for the Au(dmit)2 and Ni(dmit)2 materials are obtained. Simultaneously, combining the concentration of the sample, the molecular second-order hyperpolarizability are calculated. And we find the application field for each material. The Au(dmit)2 materials can applied to AOS and the Ni(dmit)2 materials have potential applications in saturable absorber.Fourthly, in order to optimize the third-order NLO properties for the Au(dmit)2 materials and increase their practical value in AOS field, we filter out the PrAu materials with the most excellent comprehensive performance and prepared PrAu/ PMMA composite film with spin-coating method. The third-order NLO properties are analyzed with Z-scan technique.under the condition of 1064 nm,20 ps laser. Comparing the experimental results for the PrAu solution and PrAu film, we find that the properties of the PrAu material are very stable on both solution and film forms. The third-order nonlinear refractive index n2 and the third-order nonlinear susceptibilityχ(3) of the film is three order of magnitude higher than that of the solution, indicating that the third-order NLO properties of film are significantly improved compared with solution. In addition, it is found that this material has strong off-resonance NLO susceptibility, satisfying the requirements of two quality factors for the AOS device (W=n2I0/α0λ, T=βλ/n2 and |W|>>1,|T|<<1).In summary, the dmit complexes have good third-order NLO properties. And it is suggested that these dmit complexes are promising candidates for applications to nonlinear optical devices manufacture in the near-infrared waveband.The authors acknowledge the financial support of the National Natural Science Foundation (Grant Nos.60778037,11004123 and 50772059) and the Foundation for the Author of National Excellent Doctoral Dissertation of P. R. China (No.200539). |
PDF Full Text Request