David B. Chung

High-Efficiency, Liquid-Crystal-Based, Controllable Diffraction Grating

We propose a new reflective liquid-crystal diffraction grating design attained by combining the use of a polymer wall to reduce the detrimental effect of the fringing electric field in a high-resolution grating and a quarter-wave plate to make the device polarization independent. This design could offer significant performance advantages in a projection display system. Results of calculations are compared with experimental data.

Long Term Bistable Twisted Nematic Liquid Crystal Display and Its Computer Simulations

The multidimensional alignment (MDA) technique realized by the polymer wall has been previously proposed as a means to stabilize the liquid crystal configurations for twist angles of 0 and 2π so that very low power and real bistable twisted nematic (BTN) liquid crystal display (LCD) can be obtained. In this study, a two-dimensional liquid crystal director simulation software was employed to explore the stability of BTN devices. The simulation results showed that the homeotropic aligned polymer wall will stabilize the BTN device when the ratio of d/p is close to the switching d/p ratio, but when the d/p ratio is higher than 0.9, the director field will convert the configuration from a high-energy 0 twist state to low-energy 2π twist state automatically, therefore the BTN bistability will be destroyed.

29.2: Reflective Polarization Independent LC Phase Modulator with Polymer Wall

In this paper, we propose a new reflective LC phase modulator design by combining the advantage of the polymer wall to reduce the fringe field and an incorporated QWP to make the device polarization independent. This new design has promising application in the projection system, since the resolution and brightness of current LCoS projector will be limited by the fringe field and diffraction effect, while this new design is utilizing the diffraction effect and immune to the fringe field effect. We fabricate a diffractive cell, and the experiment result shows the device is polarization independent and yields high diffraction efficiency.

50.2: 2‐D Modeling of the Effect of Electrode Topography and Interpixel Gap on LCoS Devices

While there has been considerable modeling of the walls that can form in a LCOS device due to the fringing fields around the pixel electrodes, the procedures often have used simplifications. The importance of understanding these walls when very small pixels are considered has motivated us to look at some of the often-made assumptions more carefully. In this paper we model the wall due to fringing fields taking into account the topography of the electrodes and pretilt angle, and the optical effect is modeled using the Finite Difference Time Domain (FDTD). The interpixel gap on the non-ideal light reflection is also studied.

Poincare Sphere Analysis of Reflective Liquid Crystal Device

In this paper, we explain the design principle of a reflective liquid crystal device using Poincare sphere analysis. The evolution of the polarization state of light progressing through the liquid crystal layer and a compensator is shown. The analysis method provides a device optimization procedure that follows clearly from the effect of device parameters on the polarization state of light.

Alternative dynamics for the symmetric splay to bend transition in a nematic liquid crystal layer

A pathway for a coherent topological transition from the splay to bend director configuration in liquid crystal layers has been previously described via order reconstruction in a two‐dimensional sheet in the plane of the liquid crystal layer. In this paper we provide the details of the modelling of an alternative pathway that is based on the nucleation, motion and annihilation of an array of disclination lines. Electrical current flow onto the cell is calculated based on the two pathways and compared with data.

62.5L: Late-News Paper: Two-Dimensional Dynamic Modeling of Splay to Bend Transition in Pi Cell or BTN Device at High Voltage

A bulk transition from the splay to bend state resulting from the application of a high voltage to a layer of liquid crystalline material has been previously observed experimentally, and has been explained as a reconstruction of the order in a two dimensional sheet near the center of the layer. In this paper, we propose an alternative explanation of the transition that includes defect nucleation and movement resulting from a very small periodic distortion of the director field in the plane of the considered layer. The dynamics of this alternative transition are shown through two-dimensional dynamic modeling of the director field. Our simulation results show that this transition process occurs preferentially over the bulk order reconstruction predicted by one-dimensional modeling.

28.4: Poincare Sphere Analysis of LCOS E-O Effects

LCoS imager performance depends on the liquid crystal (LC) operation mode that is being selected. In this paper we explain the design principle in an alternative way by using Poincare sphere analysis. The selection of the compensator parameters for the LC modes, which need to be compensated to get good dark state, is also discussed by using Poincare sphere analysis. We also introduce the plotting of reflectivity vs. retardation(Δnd /λ) with bright state and black state plotted on the same graph, which we found is very helpful for mode selection.

31.3: A New Type of Liquid Crystal Diffractive Light Valve with Very Small Pixel Size

Polymer wall confined switchable diffractive liquid crystal light valve is investigated by two-dimensional finite-difference time-domain (FDTD) optical simulations and liquid crystal director calculations. The calculated brightness vs. device pixel size and the number of turn “ON” pixels are provided. The results indicate that this kind of device is very promising candidate for high resolution and high brightness projection displays.