Nonlinear Optics in Single Crystal Microstructures of Organic Materials

该项目的主要目标是利用特定有机单晶薄膜的大非共振非线性折射率来证明皮秒全光逻辑和光学双稳性。整个项目的目标包括：i)制备单晶薄膜和有机二阶和三阶光学材料的器件微结构，ii)详细研究薄膜的非谐振非线性，以及iii)演示包括波导中相位匹配SHG，全光和电光开关和逻辑的器件。非线性光学研究将包括偏振相关的SHG和二阶光学薄膜中的电光效应，以及三阶光学薄膜的时间和波长分辨非线性折射率测量。涉及非谐振三阶过程的机制将被阐明，皮秒全光逻辑将使用特定的有机材料和器件几何形状进行演示。利用非常大的二阶非线性的有机薄膜，电光开关和逻辑将被展示。特定的共轭聚合物，如聚二乙炔，在非共振域具有非常大的非线性折射率和低的吸收系数。只有当聚合物链以单晶形式组织时，才能获得如此大的非线性。特定的有机分子晶体（如NPP， DAST）具有非常大而稳定的二阶非线性，如果可以制备单晶膜和波导，可以用于许多应用（如用于红外二极管激光器的SHG，电光开关）。主要研究者建立的一种方法（“剪切法”及其改进版本）将用于制备有机二、三阶光学材料的单晶薄膜。随后，将利用该薄膜制备法布里-珀罗标准子和波导几何单元中的特定器件微结构。薄膜和波导中的非线性光学测量将使用既定的程序进行。最近，我们已经证明了全光开关使用的关闭共振非线性的聚二乙炔薄膜，放置在一个法布里-珀罗腔。测量的开关时间受到所使用的脉冲宽度（30ps）的限制。涉及全光逻辑和双稳性的详细测量将在这项拟议的工作中使用！皮秒和亚皮秒脉冲。超快全光开关和逻辑在一个紧凑的器件几何应该有各种光子学的未来应用。具有很大二阶非线性的有机材料单晶薄膜和波导有望在近期的频率转换和电光中得到应用。提出的研究对于从根本上理解这些非谐振非线性光学效应和实现许多实际应用具有重要意义。＊＊＊

9634268 Thakur A major objective of this project is to demonstrate picosecond all-optical logic and optical bistability using the large off-resonant nonlinear refractive indices of specific organic single crystal films. The overall project objectives include: i) preparation of single crystal films and device microstructures of organic second and third order optical materials, ii) detailed studies of the off-resonant nonlinearities of the films and, iii) demonstration of devices including phase-matched SHG in waveguides, all-optical and electro-optic switching and logic. The nonlinear optical studies will include polarization dependent SHG and electro-optic effects in second order optical films and time and wavelength resolved nonlinear refractive index measurements for the third order optical films. The mechanisms involved in the off-resonant third order processes will be elucidated and picosecond all-optical logic will be demonstrated using specific organic materials and device geometries. Utilizing organic films of very large second order nonlinearities, electro-optic switching and logic will be demonstrated. Specific conjugated polymers such as polydiacetylenes are known to have extremely large nonlinear refractive indices along with low absorption coefficients in the off-resonant domain. Such large nonlinearities are obtained only if the polymer chains are organized as a single crystal. Specific organic molecular crystals (e.g. NPP, DAST have very large and stable second order nonlinearities which can be utilized in many applications (e.g. SHG for infrared diode lasers, electrooptic switching), if single crystal films and waveguides can be prepared. A method ("shear method" and its modified version) that the principal investigator has established, will be utilized for the preparation of single crystal films of the organic second and third order optical materials. Subsequently specific device microstructures in the Fabry-Perot etalon and waveguide geom etries will be fabricated using the films. The nonlinear optical measurements in the films and waveguides will be performed using established procedures. Recently, we have demonstrated all-optical switching using the off- resonant nonlinearity of a polydiacetylene film, placed in a Fabry-Perot cavity. The measured switching time was limited by the pulse-width (30ps) that was used. Detailed measurements involving all-optical logic and bistability will be performed in this proposed work using ! picosecond and sub-picosecond pulses. Ultrafast all-optical switching and logic in a compact device geometry should have a variety of future applications in photonics. Single crystal films and waveguides of organic materials having very large second order nonlinearities are expected to have near-term applications in frequency conversion and electro-optics. The research as proposed is important for fundamental understanding of these off-resonant nonlinear optical effects and for realizing many practical applications. ***