新型快速响应液晶特性及应用研究

发布时间：2018-05-18 06:15

本文选题：蓝相液晶 + 高分辨率　；参考：《东南大学》2016年博士论文

【摘要】：液晶既具有晶体的各向异性又具有液体的流动性,被广泛的应用于显示、相位调制、信息存储、光开关和光通信等领域,并对自适应光学、集成光学的发展起到极大的促进作用。但是,传统的向列相液晶电光器件,响应时间较长,通常在毫秒量级,甚至长达秒量级,限制液晶型电光器件的进一步发展。蓝相是一种介于各向同性相和胆甾相之间的特殊液晶相态,具有亚毫秒量级的快速响应速度,在新一代液晶显示器、电控焦距可调液晶透镜、液晶光栅、空间光调制器等电光器件中具有广泛的应用前景。因此,本文围绕新型快速响应的液晶电光器件展开研究,旨在采用新型的快速响应液晶材料,研究其电光特性,针对蓝相液晶器件的驱动电压高、效率低等问题,设计和制备新型结构的电光器件,实现低工作电压,快速响应,高效率的蓝相液晶电光器件。本文主要研究工作和成果概括如下：1.聚合物稳定的蓝相液晶材料制备及电光特性的研究。聚合物稳定的蓝相液晶一般包含三种主要成分：作为转动分子的向列相液晶母体,提供螺旋力形成蓝相态的手性剂和形成稳定网络结构的聚合物单体。通过在一定的温度下进行紫外光固化,可以得到聚合物稳定的蓝相液晶。采用上述方法,我们成功制备了均匀的聚合物稳定的蓝相液晶,拓宽蓝相液晶温宽范围至包含室温在内的-20℃-62℃。进而,我们改变手性剂的含量,调节蓝相液晶布拉格反射峰中心波长的峰值,得到不同布拉格反射峰的聚合物稳定的蓝相液晶材料,反射峰半波宽在几十纳米量级。同时,我们也研究了各材料组分对蓝相液晶电光特性的影响。在此基础上,我们对不同聚合物单体含量的聚合物稳定的蓝相液晶进行了动态响应特性测试及分析,从而解释了聚合物稳定的蓝相液晶材料的亚毫秒响应特性及迟滞效应的产生机理。2.高分辨率蓝相液晶相位调制器件的研究。超高分辨率和快速响应速度是液晶电光器件不断追求的目标。随着分辨率的不断提高,边缘电场效应(Fringing Electric Field Effect)和响应时间成为液晶相位调制器件发展的主要制约因素。针对这两个制约因素,本文首先对超高分辨率向列相液晶相位调制器的边缘电场效应进行了系统的研究。继而,将聚合物稳定的蓝相液晶与超高分辨率反射型液晶相位调制器件相结合,以实现亚毫秒快速响应的液晶相位调制器件。在此基础上,研究边缘电场效应对超高分辨率聚合物稳定的蓝相液晶相位调制器件调制性能的影响,提出了在边缘电场作用下,蓝相液晶相位调制器件是偏振相关的,优化材料及结构参数,首次提出采用科尔系数且高饱和折射率的蓝相液晶材料,优化盒厚,能够有效降低器件工作电压,为聚合物稳定的蓝相液晶相位调制器件的实现提供理论基础。进一步,为了克服聚合物稳定的蓝相液晶的高电压缺点及材料依赖性,并且解决超高分辨率下边缘电场效应带来的相位偏移,我们设计新型的蓝相液晶相位调制光学系统,成功地降低驱动电压至26.09 V,为实现硅基TFT驱动的反射型蓝相液晶器件提供了可能。同时该系统能够自动补偿边缘电场效应带来的相位偏移,有效改善超高分辨率的蓝相液晶相位调制器件的调制特性,使硅基聚合物稳定的蓝相液晶(Polymer Stabilized Blue Phase Liquid Crystal on Silicon, PSBP-LCoS)相位调制器件成为可能。该成果已经发表在期刊Optics Express和Applied Optics上。3.设计并制备了高衍射效率亚毫秒响应的蓝相液晶可调光栅。为了克服传统向列相液晶可调光栅偏振依赖、响应时间长和衍射效率低的不足,我们将蓝相液晶与聚合物条状光栅技术结合起来,设计并且制备了新型结构的聚合物稳定的蓝相液晶可调光栅。该新型结构利用毛细作用力将蓝相液晶灌入聚合物条状结构的间隙中,得到理想的矩形光栅相位面分布,远场偶级次衍射效率基本为零,±1级最大衍射效率达38%,并且加电可调。同时,该光栅具有偏振无关和亚毫秒的快速响应速度。该成果已经发表在期刊Journal of Applied Physics上。4.设计并制备了双周期蓝相液晶可调光栅。针对现有液晶可调光栅只能对衍射角度或者衍射效率进行调节的不足,我们设计了新型的光栅结构,通过选择不同的驱动方式,可以实现对衍射角度大小的控制,并且在每一个衍射角度下,衍射效率都可以由外加电压来调节,小周期光栅±1级最大衍射效率达35.3%,大周期光栅±1级最大衍射效率为28.7%,同时该新型结构的光栅具有偏振无关和近亚毫秒的快速响应速度,通过控制驱动方式,可以在时序上得到5个转换口(Fan-out/Coherent),在光通信领域具有巨大的的应用潜力。该成果已经发表在期刊Optics Letters上。
[Abstract]:Liquid crystals have both the anisotropy of crystal and liquid flow, which are widely used in the fields of display, phase modulation, information storage, optical switching and optical communication, and play a great role in the development of adaptive optics and integrated optics. However, the traditional nematic liquid crystal electro-optic devices have a long response time, usually in milliseconds. The order of magnitude, or even the magnitude of the second, limits the further development of the liquid crystal optical devices. The blue phase is a special liquid crystal phase between the isotropic phase and the cholesteric phase. It has a fast response speed of sub millisecond magnitude. In the new generation of liquid crystal displays, electrically controlled focal length tunable liquid crystal lens, liquid crystal grating, spatial light modulator and other electro-optical devices. In this paper, a new fast response liquid crystal electro-optical device is studied in this paper. The purpose of this paper is to use a new type of fast response liquid crystal material to study the electro-optical characteristics. In view of the high driving voltage and low efficiency of the blue phase liquid crystal devices, the design and preparation of a new type of electro-optic devices to realize low working voltage. Fast response and efficient blue phase liquid crystal electro-optic devices. The main research work and achievements are summarized as follows: 1. the preparation of stable blue phase liquid crystal materials and the study of the electro-optic characteristics. The polymer stabilized blue phase liquid crystal usually contains three main components: the nematic liquid crystal matrix as a rotating molecule, which provides the spiral force formation blue. The phase of the chiral agent and the polymer monomer forming stable network structure. By UV curing at a certain temperature, a stable polymer blue phase liquid crystal can be obtained. Using the above method, we successfully prepared a uniform polymer stable blue phase liquid crystal, and widened the temperature range of the blue phase liquid crystal to -20 C -62, including room temperature. At the same time, we change the content of the chiral agent and adjust the peak of the central wavelength of the Prague reflection peak in the blue phase liquid crystal, and get the stable polymer blue phase liquid crystal material with different reflection peaks of the Prague. The reflection peak half wave width is at the order of dozens of nanometers. Meanwhile, we also study the influence of the material components on the electrooptic characteristics of the blue phase liquid crystal. At the same time, we test and analyze the dynamic response characteristics of the stable blue phase liquid crystals with different polymer monomers content, which explains the sub millisecond response characteristics and the mechanism of the hysteresis effect of the polymer stabilized blue phase liquid crystal material.2. high resolution blue phase liquid crystal phase modulation device. The fast response speed is the goal of the liquid crystal optical devices. With the continuous improvement of the resolution, the edge electric field effect (Fringing Electric Field Effect) and the response time are the main constraints for the development of liquid crystal phase modulation devices. In this paper, the phase modulation of the ultra high resolution nematic liquid crystal is first introduced. The edge electric field effect of the device is systematically studied. Then, the liquid crystal phase modulation devices with the fast response to the sub millisecond are realized by combining the polymer stabilized blue phase liquid crystal with the ultra high resolution reflective liquid crystal phase modulator. On this basis, the blue phase liquid crystal phase of the ultra high resolution polymer is studied by the edge electric field effect. Under the influence of the modulation performance of the bit modulation device, it is proposed that blue phase liquid crystal phase modulation devices are polarization dependent, optimize material and structure parameters under the effect of edge electric field. The blue phase liquid crystal materials with Cole coefficient and high saturation refractive index are first proposed to optimize the box thickness, which can reduce the voltage of the device and stabilize the blue phase of the polymer. The realization of liquid crystal phase modulation devices provides a theoretical basis. Further, in order to overcome the high voltage defect and material dependence of the blue phase liquid crystal stabilized by the polymer, and to solve the phase shift caused by the edge electric field effect at ultra high resolution, we design a new phase modulation optical system with blue phase liquid crystal, which successfully reduces the drive voltage to the high resolution. 26.09 V, it is possible to realize the reflective blue phase liquid crystal device driven by silicon based TFT, and the system can automatically compensate the phase shift caused by the edge electric field effect, improve the modulation characteristics of the blue phase liquid crystal phase modulation device with ultra high resolution, and make the Polymer Stabilized Blue Phase Li stabilized by the silicon based polymer. The quid Crystal on Silicon, PSBP-LCoS) phase modulator is possible. The results have been published in the Journal Optics Express and Applied Optics on.3. design and prepared a blue phase tunable grating with high diffraction efficiency submillisecond response. In order to overcome the polarization dependence, response time and diffraction efficiency of conventional nematic liquid crystal tunable grating The blue phase liquid crystal tunable grating with a new structure is designed and prepared by combining the blue phase liquid crystal with the polymer bar grating. The novel structure is used to use the capillary force to fill the gap between the blue phase liquid crystal into the polymer strip structure and obtain the ideal phase surface distribution of the rectangular grating and the far field couple. The diffraction efficiency of the gradation is basically zero, the maximum diffraction efficiency of the 1 grade is 38%, and the addition of electricity is adjustable. At the same time, the grating has a polarization independent and fast response speed of sub millisecond. The results have been published on the Journal Journal of Applied Physics to design and prepare a double periodic blue phase liquid crystal tunable grating. In order to adjust the diffraction angle or the diffraction efficiency, we designed a new type of grating structure. By choosing different driving modes, we can control the diffraction angle, and at each angle of diffraction, the diffraction efficiency can be adjusted by the applied voltage, and the maximum diffraction efficiency of the small periodic grating is 35.3%, The maximum diffraction efficiency of the large periodic grating + 1 is 28.7%. At the same time, the grating of the new structure has the polarization independent and fast response speed of near submillisecond. By controlling the driving mode, it can get 5 conversions (Fan-out/Coherent) on the time series. It has great potential application in the field of optical communication. The results have been published in the Journal Optics On Letters.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN104.3

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