This paper presents a novel single-ended disturb-free 9T subthreshold SRAM cell with cross-point data-aware Write word-line structure. The disturb-free feature facilitates bit-interleaving architecture, which can reduce multiple-bit upsets in a single word and enhance soft error immunity by employing Error Checking and Correction (ECC) technique. The proposed 9T SRAM cell is demonstrated by a 72 Kb SRAM macro with a Negative Bit-Line (NBL) Write-assist and an adaptive Read operation timing tracing circuit implemented in 65 nm low-leakage CMOS technology. Measured full Read and Write functionality is error free with V down to 0.35 V ( 0.15 V lower than the threshold voltage) with 229 KHz frequency and 4.05 µW power. Data is held down to 0.275 V with 2.29 µW Standby power. The minimum energy per operation is 4.5 pJ at 0.5 V. The 72 Kb SRAM macro has wide operation range from 1.2 V down to 0.35 V, with operating frequency of around 200 MHz for V around/above 1.0 V. Index Terms-Low power, low voltage, negative bit-line (BL), subthreshold SRAM cell, timing tracing.

An electrically tunable-focusing and polarizer-free liquid crystal (LC) lens for ophthalmic applications is demonstrated. The optical mechanism of a LC lens used in human eye system is introduced. The polarizer-free LC lens for myopia-presbyopia based on artificial accommodation is demonstrated. The continuously tunable-focusing properties of the LC lenses are more practical in applications for different visional conditions of people. The concept we proposed can also be applied to another types of lenses as long as the focusing properties are tunable. The concept in this paper can also be extensively applied to imaging systems, and projection systems, such as cameras in cell phones, pico projectors, and endoscopes.

We demonstrate a hysteresis-free polymer-stabilized blue phase liquid crystals (PSBP-LCs) using thermal recycles by means of enlarging the domain size of PSBP-LC and improving the uniformity of the crystal orientations of PSBP-LC. The crystal growth of PSBP-LCs bases on a competition between the heterogeneous nucleation and the homogeneous nucleation is also demonstrated and discussed. This study opens a new window for understanding the hysteresis of the PSBP-LC and assisting in designing many PSBP-LC-based photonic devices, such as displays, electrooptical switches, and electrically tunable focusing LC lenses.

An electrically tunable pico-projector adopting a liquid crystal (LC) lens as an active optical element is demonstrated. The focal length of this picoprojector is electrically tunable from 350 to 14 cm and the tunable range is even wider than that of a manually focused pico-projector. The response times of turn-on and turn-off are approximately 313 and 880 ms, respectively. In addition, the location of the projection lens can affect the electrically tunable range of the system. A small shift of the projection lens results in the large tunable focusing range of the pico-projector and a tunable focusing range is determined by the LC lens. The optical analysis is also discussed. This concept can even be applied to design other electrically auto focusing pico-projectors based on other optical elements such as liquid lenses and spatial light modulators.

An electrically tunable focusing LC lens with a low voltage and simple planar electrodes is demonstrated. The inhomogeneous electric field of the LC lens without any hole-patterned-electrode is generated by using an embedded polymeric layer with a gradient distribution of dielectric constants (or relative permittivity). LC directors in the LC layer experience spatially inhomogeneous voltages even though a single voltage is applied to the planar electrodes. Such a LC lens has a low voltage (~2.6 V(rms)) and simple design of electrodes. The gradient distribution of dielectric constants of polymeric layer is discussed and the performance of the LC lens is investigated. The applications of such a LC lens are cell phones, webcam, and pico projectors.

An augmented reality (AR) system involving the electrically tunable location of a projected image is implemented using a liquid-crystal (LC) lens. The projected image is either real or virtual. By effectively doubling the LC lens power following light reflection, the position of a projected virtual image can be made to vary from 42 to 360 cm, while the tunable range for a projected real image is from 27 to 52 cm on the opposite side. The optical principle of the AR system is introduced and could be further developed for other tunable focusing lenses, even those with a lower lens power. The benefits of this study could be extended to head-mounted display systems for vision correction or vision compensation. We believe that tunable focusing LC optical elements are promising developments in the thriving field of AR applications.

Conventional endoscopic systems consisting of several solid lenses suffer from a fixed and limited depth-of-field (DOF). For practical applications, conventional endoscopes mechanically change the distance between the solid lenses of a lens module in order to change the focusing plane and DOF to see clearly in a scene. In this paper, we demonstrate an electrically tunable endoscopic system adopting a liquid crystal lens. By means of tunable focusing properties of the LC lens as a positive lens and a negative lens, the object at different objective distances can be imaged to the image sensor clearly and the corresponding depth-of-field can also help to enlarge the total spatial depth perception in a scene. The optical mechanism is discussed. In the experiments, under adjustment of three discrete lens powers of the LC lens, the viewing range or total spatial depth perception of the endoscopic system is from 76.4 mm to 12.4 mm which is 2x improved compared to the conventional one without LC lens. We believe this study can be extended to the applications of industrial and medical endoscopes.

A polarizer-free flexible and reflective electro-optical switch using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures due to domain sizes of polymer networks. Such flexible electro-optical switch is bendable and trim-able because of the vertical polymer networks and gel-like materials. The dye-doped LC gel shows good reflectance ~55%, good contrast ratio~450:1 and fast response~6.4 ms at curing temperature 10 degrees C. The bending curvature is 21 mm. The dye-doped LC gels open a new window for trim-able electronic papers, decorative displays, electrically switchable curtains, and electrically switchable sun control film for the automobiles, homes or commercial buildings.