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首页> 外文学位 >Realizing a fractional volt half-wave voltage in Mach-Zehnder modulators using a DC biased push-pull method, and, Synthesis and characterization of indole based NLO chromophores for improving electro-optic activity.
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Realizing a fractional volt half-wave voltage in Mach-Zehnder modulators using a DC biased push-pull method, and, Synthesis and characterization of indole based NLO chromophores for improving electro-optic activity.

机译：使用直流偏置推挽法在Mach-Zehnder调制器中实现分数伏特半波电压，以及基于吲哚的NLO发色团的合成和表征，以改善电光活性。

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The main focus of the current research has been to improve the performance of the waveguide based Electro-optic (EO) photonic devices, namely, Mach-Zehnder interferometers. These devices were poled in a Push-Pull configuration in a DC biased fashion to reduce the drive voltage (Vpi) and also to carry out the real time study of the EO activity. Under such a DC condition, sub one volt value of Vpi has been achieved at optimum poling conditions, which afforded the second lowest value of Vpi ever observed for waveguide EO devices available in the literature. Using the statistical model for the chromophore order parameter, the third order contribution under the optimum poling condition was calculated and was found to be negligible in comparison with the EO effect.; To improve the thermal stability and the optical loss, novel hybrid Mach-Zehnder devices were fabricated using sol-gel composites synthesized by modified procedures. The bottommost thicker layer of sol-gel enabled the smooth transition of the coupled light into the EO layer and light propagation was nearly adiabatic with the total device loss less than 5 dB for a 3 cm device. Although these devices showed 12.8 V of Vpi, it can be further reduced by using a better EO polymeric system having higher EO coefficient.; Attenuated Total Reflection (ATR) was set up to measure EO coefficients in thin films. Besides the ease of sample preparation and measurement, ATR enabled the measurements of EO coefficients independently and it could assess the piezoelectric contribution which was shown to be less than 3% in comparison with EO effect.; Novel chromophores containing indole as a bridge unit and different acceptors were synthesized successfully and the experimental hyperpolarizabilities were compared with those of computational results using DFT which showed promising hyperpolarizability values in comparison with the standard chromophroe EZ-FTC. However the break in the conjugation between aniline donor and acceptor through an indole unit probably caused the lower experimental hyperpolarizability, as measured by HRS technique. Better functionals than PBE, such as B3LYP though expensive, was found to be needed for geometry optimization in these calculations, which gave more reliable results.
机译：当前研究的主要重点是改善基于波导的电光（EO）光子设备的性能，即Mach-Zehnder干涉仪。这些设备以直流偏置的方式以推挽式配置极化，以降低驱动电压（Vpi），并进行EO活性的实时研究。在这样的直流条件下，在最佳极化条件下已经获得了低于1伏特的Vpi值，这为文献中的波导EO设备提供了有史以来第二低的Vpi值。使用生色团阶数参数的统计模型，计算了最佳极化条件下的三阶贡献，并且与EO效应相比可忽略不计。为了提高热稳定性和光学损耗，使用通过改进程序合成的溶胶-凝胶复合材料制造了新型混合Mach-Zehnder器件。溶胶-凝胶的最底层最厚的层使耦合的光平稳过渡到EO层，并且光的传播几乎是绝热的，对于3 cm的器件，总器件损耗小于5 dB。尽管这些器件显示出12.8 V的Vpi，但可以通过使用具有更高EO系数的更好的EO聚合物系统进一步降低它。设置衰减全反射（ATR）以测量薄膜中的EO系数。除了易于样品制备和测量外，ATR还可以独立测量EO系数，并且可以评估压电效应，与EO效应相比，压电效应小于3％。成功地合成了以吲哚为桥单元和不同受体的新型发色团，并将实验的超极化率与使用DFT的计算结果进行了比较，与标准发色团EZ-FTC相比，DFT显示出有希望的超极化率。然而，如通过HRS技术所测量的，通过吲哚单元的苯胺供体与受体之间的共轭的断裂可能导致较低的实验超极化性。在这些计算中，发现几何优化需要比PBE更好的功能，例如B3LYP，尽管价格昂贵，但可以提供更可靠的结果。

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