电控聚合物分散液晶变焦全息透镜制作

介绍了相位型全息聚合物分散液晶(PDLC)材料全息透镜,在电场作用下液晶微滴折射率逐渐与聚合物折射率匹配,实现透镜电控变焦。研究了微米尺寸和纳米尺寸液晶微滴聚合物分散液晶材料配方特性和微观结构。采用优化纳米尺寸材料配方制作5~6μm聚合物分散液晶盒,采用离轴式平面波和球面波干涉全息写入光路,成功制作电控变焦聚合物分散液晶全息透镜样品。该透镜样品焦距为20 mm,能够正一级衍射放大成像。实现“0”,“1”变焦的驱动电压阈值为60 V。并进一步提出了基于聚合物分散液晶电控变焦元件集成叠加技术实现电控变焦光学成像系统的技术思路。     

氮氧化硅/聚合物混合集成低功耗可变光衰减器

利用具有相反热光特性的氮氧化硅与聚合物材料,采用混合集成波导结构设计了一种低功耗S型可变光衰减器.该衰减器以聚合物为芯层材料,氮氧化硅为包层材料,在弯曲波导上方制作加热电极从而通过热光效应来实现可调谐的衰减功能.理论分析表明,对于1.55μm的工作波长,衰减器实现50dB的衰减仅需要3.6mW的功率.实验结果可实现0~40dB的衰减范围,相应的最大温度变化为70.4℃,器件插入损耗为5.4dB.     

波导侧壁起伏对聚酰亚胺波导光学梳状滤波器串扰特性的影响及其改善方法

提出了一种结构模型来分析由工艺引起的波导侧壁起伏对于聚合物波导光学梳状滤波器的滤波特性的影响。含氟聚酰亚胺高分子聚合物制备多级马赫一曾德尔串联型光学梳状滤波器件的工作参量为中心波长1550nm,波长间隔为0．8nm,40通道的波长交错分离。模拟计算：表明,对由高分子聚合物材料制备的多级马赫-曾德尔串联型光学梳状滤波器件,其主要影响是增大了信道之间的串扰,中心波长1550nm处的信道串扰由理想情况下的-40dB降为-12dB,极大地影响了器件的性能。在此基础上,提出一种改善光学梳状滤波器串扰性能的新结构,该结构由多级马赫-曾德尔耦合器和微环共振滤波器串接构成,40个通道的串扰改善为-0dB以下。     

应变液晶的负压光效应和反式压光效应

介绍聚合物分散液晶和应变液晶概念,给出聚合物分散液晶调光玻璃的"正压光效应"、"负压光效应"和"反式压光效应"三种效应定义.实验制备出负压光效应和反式压光效应新型应变调光玻璃样品,测试样品散射态雾度90%以上,半透明态透光率接近30%.用偏光显微术研究压光效应原理,表明对样品施加垂面按压或拉伸的应力诱导作用会引起液晶微滴中液晶分子具有某些特殊排列方式,导致样品光学性质发生显著变化.建立垂面拉伸液晶微滴模型,计算模拟所绘出的图形与偏光显微镜照片独特花样十分相似,进而合理解释了实验现象.应变液晶压光效应研究具有聚合物分散液晶基础研究意义和开发非电控调光玻璃的实际应用价值.     

电控聚合物分散液晶全息透镜及特性研究

报道位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜的研制及特性研究,理论上,根据耦合波理论,研究了不同的相分离程度系数下,理想位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜在可见光波长(400—800nm)的衍射特性.实验研制了衍射效率最高为70%的电控H-PDLC变焦透镜样品,研究表明H-PDLC透镜具有优良的成像特性,和快速响应的电控开关特性,在光学成像系统,光通信系统中具有良好的应用前景.     

基于聚合物分散液晶全息光栅的可调增益均衡器

从理论和实验两方面分析研究了聚合物分散液晶全息光栅在632.8 nm光波的入射下的衍射谱特性和电压可调特性，实验结果与耦合波理论的计算结果具有很好的一致性，从实验上验证了用耦合波理论来描述聚合物分散液晶全息光栅的衍射特性是恰当的.并且提出了利用聚合物分散液晶全息光栅对掺饵光纤放大器增益谱进行平坦化的方法，利用聚合物分散液晶全息光栅的电压可调特性可实现动态增益均衡.运用该方法，可使掺饵光纤放大器在C波段1530~1560 nm内，温度在0℃~65℃范围内变化，掺饵光纤放大器自发辐射谱的不平坦度从3.3 dB降到0.2 dBp－p（峰-峰值）.     

紫外固化型聚合物高阶布拉格波导光栅滤波器

利用紫外固化材料SU-82005与热交联聚合物甲基丙烯酸甲酯一甲基丙烯酸缩水甘油酯[P（MMA—GMA）]分别作为波导芯层和包层材料,通过直接光刻技术,成功实现了厚度为5μm,宽度为9μm,光栅高度为4μm的起伏型高阶布拉格波导光栅滤波器。对光栅器件的谐振波长,光透射率等重要参数进行了模拟设计。测得制备的聚合物高阶布拉格波导光栅滤波器的谐振波长为1550．4nm,消光比为23dB,3-dB带宽为2nm。     

1550nm工作波长新颖结构细径偏振保持光纤的制备及性能研究

对工作波长在1550nm，新型结构细径偏振保持光纤的制备与性能进行研究，并制备出拍长达到2．1mm、消光比达到28dB（1km）、工作波长在1550nm、低衰减且高强度的细径偏振保持光纤．     

高品质因子聚合物波导微环谐振腔滤波器

基于紫外固化胶和聚砜聚合物材料体系,采用脊形单模波导结构,理论设计并优化了聚合物波导环形谐振腔滤波器的波导截面参数、弯曲半径和耦合区波导间距等结构参数,分析了其滤波响应特性.并在此基础上,结合光刻、反应离子刻蚀等传统的微加工工艺制备了聚合物环形谐振腔滤波器,并进行了光谱测试,器件测试结果与设计基本符合.结果表明,该聚合物微环谐振腔滤波器在通信波段1550 nm附近的自由光谱范围为0.21 nm,3 dB带宽为0.04 nm,插入损耗为26 dB,消光比达到了11 dB,品质因子达到了3.87×104.该聚合物微环谐振腔滤波器可以用于光通信及光传感集成芯片.     

便携式电控聚合物分散液晶全息透镜的电源及结构设计

根据聚合物分散液晶材料的光电特性及需要,在研究基于聚合物分散液晶光电器件时必须设计合适的电源驱动系统。介绍了在电控聚合物分散液晶全息透镜器件研制中,将电池输出的直流低压升高变频到70～100V、1000Hz频率交流高电压的电路系统设计。并介绍了变焦透镜装置总体结构的机械设计。实验结果表明,该电源设计能够满足聚合物分散液晶全息透镜器件中的液晶分子光轴驱动的需要,并能实现器件的小型化和便捷式。     

电压调谐液晶滤光片的研究

对以液晶为腔内物质的液晶法布里珀罗调谐滤光片进行了改进 ,在原来法布里珀罗腔的两侧各加一偏振镜 ,使两个偏振镜的起偏方向平行 ,并且偏振方向都相对于液晶分子长轴的方向成 45°角 ,入射光经多光束干涉后再经偏光干涉 ,导出其透射峰满足的条件为 2 (n∥ -n⊥)Lcosθ =mλ ,这样便克服了原有调谐滤光片两套光谱难以区分的缺点。对改进后的滤光片进行测试 ,在 15 5 0nm附近对该电调谐滤光片的滤光特性做了细致的分析     

采用接触式极化法研制有机聚合物电光光波导调制器

结合器件的整体结构考虑，对接触式极化方法和工艺进行了研究，基于接触式极化法，设计并制作了聚合物电光光波导相位和偏振调制器。通过测量器件的偏振调制特性，在1550nm光波波长下，获得了最大电光系数为llpm／V，电光相位调制器的半波电压为45V。     

Fabrication of Variable Optica l Attenuator With Low Inse rtion Loss

Avoltage -controlled variabl optical attenuator (VOA) based on silica-b a sed planar ligh t wa ve circu its (P LC) was fabricated by flame hydrolysis deposition (FHD). The variable attenuator with Cr heater achieves 20dB attenuation with 318mW electrical power at 1550 nm. The insertion loss and the polarization dependent loss (PDL) at 0 attenuation are 1dB and 0.23dB, respectively.     

Analysis of tunable codirectional vertical couplers with liquid crystal overlays for integrated dye lasers

We propose a guided-wave dye laser using a grating-assisted codirectional vertical coupler as an intracavity tunable filter. A liquid crystal overlay is designed to attain a phase-matching wavelength shift in the vertical coupler and a tunable range of over 60 nm is calculated at a center wavelength of 590 nm with a coupling efficiency of more than –1 dB. The tunable range is limited by the coupling length mismatch rather than by the refractive index variation in the liquid crystal overlay. Sidelobe level in the filter response is increased when the phase-matching wavelength is shifted to the long-wavelength side; nevertheless, the weighted coupling keeps the sidelobe-suppression ratio at more than 30 dB over a spectral span of 100 nm.     

Low threshold and high contrast polymer dispersed liquid crystal grating based on twisted nematic polarization modulator

An electrically tunable mode is proposed to overcome the bottleneck problem of a conventional polymer dispersed liquid crystal (PDLC) grating and realize its low threshold and high contrast through an alignment-controlled PDLC. The results indicate that the threshold voltage V_PP of the grating is as low as 0.75–0.8 V, the saturation voltage V_pp is 7 V and the contrast ratio of the grating reaches 245, which is about three times larger than the conventional PDLC grating. Stability testing indicates a stable state of contrast during a long time. PACS 42.40.Eq; 42.70.Df; 42.79.Kr     

Polysulfone as polymer matrix for a novel polymer-dispersed liquid crystals system

We report the preparation and thermotropic characterization of a novel polymer-dispersed liquid crystal (PDLC) system based on the polysulfone (PSU) UDEL-1700 as a polymer matrix and on 4-[4-(n-butyloxy)phenylene-imino-methylidene]benzonitrile as a liquid crystal. PDLC films have been prepared using the thermal-induced phase separation (TIPS) technique, with different compositions in the two components. A detailed optical polarized microscopy and differential scanning calorimetry study has been carried out to evaluate a correlation between the composite composition and the PDLC formation. We found that PSU could be a good matrix for the formation of PDLC systems.     

PDLC-based VOA with a small polarization dependent loss

A polymer-dispersed liquid crystal (PDLC)-based variable optical attenuator (VOA) was demonstrated to exhibit a relatively small polarization dependent loss (PDL) in the optical communication C band. The influence of the PDLC characteristics, the temperature, as well as the wavelength of the laser irradiation, on the PDLC VOA performance was analyzed. The PDL, the insertion loss at saturated voltage, and the operating voltage of the PDLC-based VOA were reduced by optimizing the fabrication conditions and applying a bias voltage to the PDLC cells during polymerization-induced phase separation.     

Tunable single- and dual-wavelength erbium-doped fiber laser based on Sagnac filter with a high-birefringence photonic crystal fiber

In this paper, we observed and experimentally investigated a high-performance single- and dual-wavelength erbium-doped fiber ring laser based on a Sagnac filter which contains a section of high-birefringence photonic crystal fiber (HB-PCF) and a polarization controller. Incorporation of the high-birefringence photonic crystal fiber can suppress multimode oscillation, improve power stability and increase the optical signal-to-noise ratio (SNR). Wavelength tunable was achieved by using a polarization controller in the Sagnac filter. Highly stable single-, dual-wavelength oscillations are tunable within a wavelength range from 1550 to 1562 nm and SNR as high as 57 dB with narrow line width about 0.011 nm, is experimentally demonstrated.     

A liquid lens-based broadband variable fiber optical attenuator

To the best of our knowledge, proposed is the first variable fiber optical attenuator (VFOA) using an electronically controlled variable focus liquid lens. The approach uses the changes in the radius of curvature of the liquid lens edge to enable an electronically controlled optical wedge that produces a varying beam tilt angle. In effect, changing beam tilt within a single mode fiber (SMF) lens free space coupling assembly leads to a polarization independent broadband VFOA design. The demonstrated VFOA experiment shows broadband operation over the 1530-1560 nm C-Band with a 40 dB dynamic range, <0.5 dB resolution, 0.3 dB polarization dependant loss, 4.3 dB fiber-to-fiber optical loss, 3 dB optical bandwidth from 1510 nm to 1700 nm, and switching time of <100 ms. Applications for this VFOA include use in hand held test and measurement equipment.