Volume 88, Issue 4, 15 August 2000
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
88(2000); http://dx.doi.org/10.1063/1.1305905View Description Hide Description
Light-induced space-charge fields and the related orientational photorefractive effects in nematic liquid crystal cells are studied both theoretically and experimentally. Analytical solutions for the refractive index change distribution are obtained under the single-elastic-constant approximation with various configurations of externally applied electric and magnetic fields and of the nematic liquid crystal director. The effects of the rigid boundary condition are investigated in detail. The grating spacing for which the refractive index change is maximized depends on the strength of external electric and magnetic fields. The responses of parallel cells differ from those of homeotropic cells, both upon the dependencies on the grating spacing and on the external fields. Under the same conditions, the orientational photorefractive effects are stronger in parallel cells than in homeotropic ones. It is also shown that the investigated effects will be greatly enhanced near the Freédericksz transition. Experimental verifications of the photorefractive response in parallel aligned cells confirm the necessity to consider the boundary conditions explicitly.
88(2000); http://dx.doi.org/10.1063/1.1303052View Description Hide Description
The contrast ratios of reflective bistable twisted nematicliquid crystal displays with a rear quarter-wave film are optimized by means of a parameter space approach. By plotting the contrast ratio as a function of the twist angle and thickness-birefringence product of the display, the regions where the displays show the best contrast ratio are clearly shown. Both the absolute reflectance and the wavelength dispersion of two bistable twisted states are investigated. It is confirmed that superhigh contrast ratio (infinite in principle), reflectance about 95% with polarized-light input, a large value (0.63 μm), and low dispersion are possible for such reflective bistable liquid crystal display.
88(2000); http://dx.doi.org/10.1063/1.1303053View Description Hide Description
A new mode of 0°–360° bistable twisted nematic (BTN) liquid crystal display is developed by using a parameter space method. This new mode possesses a large value that provides a possibility of using a 4.8–7 μm cell gap and a 6.5 V operating voltage for the new 0°–360° BTN cells. The high-contrast ratios above 80 within −80°–80° viewing-angle ranges are obtained experimentally in a horizontal direction, and the highest contrast ratio achieved is up to 250. In the contrast ratio, the experiment’s results concur with the simulation results.
88(2000); http://dx.doi.org/10.1063/1.1303054View Description Hide Description
Analytical, numerical, and experimental studies of the nonlinear transmission of a Pt:ethynyl compound have been carried out. Based on a model for the electronic transitions derived from earlier work, optical limiting behavior that is both broadband across the visible and effective over a range of pulse lengths, is predicted. Detailed experimental results are presented which exhibit many of the theoretically predicted characteristics, including a broadband nonlinear response from 450 to 700 nm.