一种采用内部线栅偏振片的半透半反射式液晶显示器

为了同时获得具有高透射率和反射率的液晶显示器,提出了一种采用内部线栅式偏振片(wiregridpolarizer,WGP)的单倍盒间距的半透半反式液晶显示器方法。在反射模式中,液晶盒内嵌的WGP作为依赖于偏振的外界光的反射器;在透射模式中,不需要消色差的四分之一波片。基于液晶盒的初始取向,该器件可用于正常显黑模式(垂直取向)和正常显白模式(扭曲向列相取向)。本文研究了这两种器件结构详细的电光特性,如电压依赖光效率特性和视角特性。     

An optically controlled liquid crystal device using azopolymerfilms

We have developed a liquid crystal (LC) device that is totally controlled using light. The initial alignment is made by optically buffing the azopolymer film with two coherent argon laser beams. Surface relief gratings have been optically induced on an assembled cell filled with LC. A single linearly polarized argon laser beam is then employed to irradiate the sample and photoinduce a twisted alignment structure. This can then be erased by a circularly polarized beam. The alignment information can also be erased by heating to the glass transition temperature of the azopolymer film     

一种宽视角和快速响应的连续视角可控液晶显示

在垂面排列液晶显示模式中,液晶分子垂直取向,具有暗态良好、高对比度的特点,但是其视角特性不佳。采用MVA和PVA技术等多畴结构可以使VA模式的视角情况得到改善,但MVA模式中凸起结构引起的液晶分子初始预倾状态会导致暗态漏光,从而降低显示的对比度。而PVA模式中的狭缝结构虽然不会影响对比度,但其响应速度比较慢。文中提出一种新型垂面排列液晶显示器结构,其像素电极四周刻蚀有弧形狭缝,公共电极中心刻蚀有孔洞。施加电压时液晶分子向中心倾倒,形成中心对称的多畴结构,实现了对比度均匀的宽视角,且这一结构在保证高透过率的同时还可以实现快速响应。另外,通过在公共电极上施加偏置电压,该结构还可实现视角的连续可控。     

采用反射式液晶显示器和有机电致发光器件前后双置组合而成的高环境对比度显示器

一种高环境对比度(A-CR)和大开口率的显示器已经从理论上证明,并通过把一个正常显黑反射型显示器(NB-RLCD)和一个有机电致发光器件(OLED)堆垛的实验加以证明。这种前后双置(以下称为tandem型)的器件组合可以分别在明亮或昏暗的环境下切换NB-RLCD模式或OLED模式。RLCD的正常显黑特性也可以提升OLED模式工作时的A-CR性能。为了在RLCD模式下获得更好的图像品质,一个复杂并且具有传输功能的结构被用于消除镜面反射和提高可视角至CR﹥2:1超过55°的锥面可视角度。另外,这样的结构也可以提高OLED49.4%的表面量子效率。在我们的实验里,忽略环境亮度因素并使A-CR保持在100:1以上。     

一种利用反射电极偏压的半反半透LCD

介绍了一种VA模式反射电极偏压的常黑单盒厚半反半透LCD.在透射区,形成连续且均匀的贯穿液晶层的电场;而在反射区,电场则主要由电极表面形状控制.由此,可使透射区的位相延迟约是反射区的2倍.这样一种半反半透LCD不论透射区还是反射区都有很高的光透过率(＞90%),同时二者灰阶特性重合度也很好.     

一种利用反射电极偏压的半反半透LCD

介绍了一种VA模式反射电极偏压的常黑单盒厚半反半透LCD。在透射区,形成连续且均匀的贯穿液晶层的电场;而在反射区,电场则主要由电极表面形状控制。由此,可使透射区的位相延迟约是反射区的2倍。这样一种半反半透LCD不论透射区还是反射区都有很高的光透过率(>90%),同时二者灰阶特性重合度也很好。     

大模场双包层光纤熔接的功率对准技术研究

为了提高高功率光纤激光器中大模场双包层光纤的熔接质量,采用NUFERN 20/400μm双包层光纤搭建了光功率对准系统,对大模场双包层光纤中存在包层光以及纤芯中只有基模和存在高阶模时光纤径向偏移与耦合效率的关系进行了理论分析和实验验证。结果表明,大模场双包层光纤中包层光和纤芯中高阶模的存在使耦合效率对径向偏移变化的敏感度降低,滤除包层光和高阶模后耦合效率随光纤径向偏移量呈高斯型变化; 使用光功率对准系统搭建千瓦级双端抽运激光系统,最大输出功率约1170W,光光转换效率约73%,光束质量约1.22,实现了千瓦级准单模输出。光功率对准技术能够实现待熔光纤的精确对准,对高功率光纤激光器输出性能的提升有重要意义。     

Nested-Ring Mach–Zehnder Interferometer in Silicon-on-Insulator

For the first time, a nested-ring Mach-Zehnder interferometer (MZI) on silicon-on-insulator is realized using a complementary metal-oxide-semiconductor-based process. In this letter, we verify that the device operates in two modes: the inner-loop resonance dominant mode due to strong build-up inside the inner-ring, and the double-Fano resonances mode due to strong light interaction with the outer loop. The results show that the inner-loop resonance is highly sensitive to the MZI arm imbalance compared to the double-Fano resonance mode. Based on these considerations, we obtain a good fit between theory and experiment.     

Silicon light emitting device in CMOS technology

A novel silicon light emitting device was realized with standard 0.35μm 2P4M Mixed Mode/RF CMOS technology. The device functions in a reverse breakdown mode and can be turned on at 8.3 V and operated normally at a wide voltage range of 8.3 V-12.0 V. An output optical power of 13.6 nW was measured at the bias of 10 V and 100 mA, and the emitted light intensity was calculated to be more than 1 mW/cm2. The optical spectrum of the device is in the range of 500-820 nm.     

High Efficiency Transflective Nematic LC Cell Using Three Director States

A new transflective nematic liquid crystal display is presented. Unlike other transflective cells, almost the entire device area is potentially available for either transmission of backlighting or reflection of ambient illumination, providing efficient use of available light for the desired application. The single cell-gap device does not require patterned alignment layers or a patterned retarder but employs planar and interdigitated electrodes. The number of electrical connections required makes the cell most suitable for low information content displays. Simulations are used to make comparisons with existing dual-gap and single-gap patterned alignment designs.      

Passive polarization converter in SiON technology

A passive polarization converter has been realized in silicon oxynitride (SiON) technology. The device is a grating assisted codirectional coupler consisting of segments of asymmetrically etched ridge waveguides. By using a double-masking technique, the fabrication of the device is tolerant with respect to the alignment of the required masks. Conversion efficiencies up to 0.98 (TE→TM and TM→TE) and insertion losses of 3 dB/cm have been measured. Using 2-D beam propagation method simulations, an observed beat pattern in the converter could be explained as due to a leaky mode, which is captured in the grating structure     

Frequency response of a unidirectional-output optical frequencyconversion device with an asymmetrical-κ DBR laser structure

The frequency response of a unidirectional-output optical frequency conversion device is measured. The device has a saturable absorber region within the active region, which acts as an optical gate for converted light. The 3-dB bandwidth of the device with saturable absorber region is measured up to 800 MHz, and is found to be limited by the frequency response of the saturable absorber region. To operate the device faster, lasing mode intensity modulation by input light is attempted by using the device in a laser diode mode. In this case, the electrodes of the saturable absorber and the gain regions are connected electrically, and the saturable absorber region is also biased far above the threshold condition at the same time with the gain region. The 3-dB bandwidth of the device increases to over 10 GHz, and the 10-Gb/s nonreturn-to-zero (NRZ) eye pattern can be observed when the input TM-polarized light intensity is modulated by a 10-Gb/s NRZ pseudorandom signal     

反射式扭曲向列相液晶显示器工作模式的演化

用动态参数空间方法研究了反射式扭曲向列相液晶显示的常白工作方式,观察到,当偏振片角度β变化时,显示从纯电控双折射（ECB）模式演化到反射式扭曲向列相模式（扭曲角为52°）。并且第一和第二ECB模式虽沿着不同路径演化,但最终合并成同一个优化反射式扭曲向列相模式。从反射式扭曲向列液晶显示模式的演化角度出发,研究了电光响应、反射率对波长的依赖关系等。     

Wide-View and Broadband Circular Polarizers for Transflective Liquid Crystal Displays

A simple wide-view and broadband circular polarizer comprising of a linear polarizer and two uniaxial films is proposed to enhance the viewing angle of transflective liquid crystal displays (LCDs). For the transmissive mode, over the entire 90deg viewing cone, the normalized light leakage from two stacked circular polarizers is suppressed to below 1.5times10^-2, and contrast ratio over 10:1 is obtained using a normally black vertically aligned transflective LCD. At the same time, this configuration warrants a broadband operation and reasonably good viewing angle (10:1 contrast ratio is over 40 at all directions) for the reflective mode. The physical mechanisms for achieving broadband operation and wide viewing angle are discussed.     

Liquid-crystal color display by DAP-TN double-layered structure

A liquid-crystal display device is reported combining a polarizer, a deformation of aligned phases (DAP) cell, a twisted nematic (TN) cell, and an analyzer in series arrangement. The color of the transmitted light can be modulated by the application of voltage to the DAP cell. The transmission properties of the device can be switched from the DAP mode for crossed polarizers to that for parallel polarizers by the application of voltage to the TN cell. This improves control of the transmitted color.     

Effect of multi-walled carbon nanotubes on electron injection and charge generation in AC field-induced polymer electroluminescence

We investigate the use of multi-walled carbon nanotubes (MWNTs) dispersed in an emissive layer of poly (N-vinylcarbazole) (PVK):fac-tris(2-phenylpyri-dine)iridium(III) [Ir(ppy)₃] in alternating current (AC) field-induced polymer electroluminescence (FIPEL) devices. A symmetric device structure, with the polymer/MWNT composite between two dielectric layers, was used to study the effect of MWNTs on charge generation within the active layer. An asymmetric device structure, using one dielectric layer, was used to study band alignment effects of carbon nanotubes in charge injection from a contact. The presence of MWNTs within the emissive layer facilitates effective internal charge generation in the symmetric devices, as would be expected if they acted as a charge source. However, electron injection under AC-driven fields also increases in the asymmetric devices, suggesting a modification to band alignment. Increase in light emission of five times is achieved in composite devices compared to devices with the pure polymer. From the trends in behavior with nanotube loading, we suggest that the nanotubes effectively doped the polymer, modifying energy level alignment in the device and increasing field-induced polarization currents. The combined effects of electron injection and charge generation may pave the way for widespread use of MWNTs in high-performance FIPEL devices.     

A High-Speed Measurement Method for Reflective Liquid Crystal Cells Using a Liquid Crystal Polarization-Converting Device

We propose a novel measurement method for determining cell parameters, such as a cell thickness and twist angle in reflective liquid crystal (LC) cells, by using a unique polarization-converting device prepared with a circularly and homogeneously aligned LC (CH-LC) cell. The light intensity distributions from the reflective LC cell transmitted twice through the CH-LC cell are measured by a charge-coupled device array camera. Cell thickness can be derived by using coordinate values of local minimum spot in the spatial light intensity distribution measured at one wavelength, where the pretilt angle is assumed to be the designed value. Both cell thickness and twist angle can also be determined by two local minimum positions of the light intensity at two different wavelengths and the effects of a quarter-wave plate are discussed     

Multiwavelength light emitters for scanning applications fabricatedby flipchip bonding

We present a multiwavelength light source which was fabricated using a self-aligned flipchip bonding technique. The device consists of an InGaN-GaN light-emitting diode emitting light at around 420 nm, on top of which we flipchip-bonded a monolithically integrated red/infrared dual-beam laser. The upper two lasers were built by selective removal of the red laser, and subsequent regrowth of an infrared laser structure. Since all processes, including the deposition of the PbSn solder bumps for bonding, were based on photolithographic precision, tight alignment tolerances of ±μm in the lateral direction could be fulfilled between the ridge waveguides of the three light emitters. For a high-speed color scanning system, this is an important design criterion because it will allow the use of a single scanning optics for the three laser beams     

Fourier transformation using an electroabsorptive CCD spatial light modulator

The use of a GaAs CCD as a spatial light modulator is described and its application to coherent optical Fourier transformation is analyzed. In this device, the transmission through the two-dimensional buried-channel CCD may be electroabsorption modulated near the GaAs cutoff wavelength since the electric field in each storage well is controlled by the transferred charge. One of the primary advantages of this modulator is the ability to electrically address the device at high speed. Analysis of the two-dimensional modulator with a silicon CCD detector array yields a projected dynamic range approximately equal to the number of modulator array elements. For arrays containing greater than 1000 elements, detector performance and nonuniformities can limit the maximum range to 30-40 dB. The device can also be optically addressed, and in this mode of operation it has a comparable dynamic range to the electrically addressed structure with an optical write energy an order of magnitude lower than liquid crystal or photorefractive light valves. An alternative mode of device operation is a waveguide mode in which the light propagates along an epitaxial layer and is modulated as it passes under a one-dimensional CCD. The detection is done by a second linear CCD. The higher modulation efficiency results in a dynamic range approximately one hundred times the number of elements but is again limited to 30-40 dB because of detector response and nonuniformities.