Volume 89, Issue 7, 01 April 2001
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
89(2001); http://dx.doi.org/10.1063/1.1351866View Description Hide Description
Illuminating a transparent mold under total internal reflection condition generates evanescent light. Near-field photolithography uses such light, and we simulated this exposure in two dimensions using the finite-difference time-domain(FDTD) method. Our simulation suggests the feasibility of resolving a 130 nm pitch grating pattern, which is finer than the diffraction limit of light. The simulation results showed fair agreement with our experimental results, confirming the strong influence of exposure light polarization to the distribution of optical near fields in photoresist films. This indicates that the FDTD simulation is promising to predict exposure results for designing molds. We further extended the simulation varying the thickness and refractive index of a photoresist film. Based on the simulation results, showing the good exposure contrast in the thin surface layer of the photoresist film, we suggested two methods to resolve a thick resist film: the multilayer resist method which allows us to use a sufficiently thin photoresist film, and the surface imaging technology which can completely dry develop a thick photoresist film even if its exposure area is confined in the surface layer.
89(2001); http://dx.doi.org/10.1063/1.1352030View Description Hide Description
A novel operating mode for a liquid crystal displaydevice has been developed. The devices involved both hybrid alignment and twisted director configuration. The operating mode was thus termed a hybrid twisted nematic (HTN) mode. In comparison with the conventional twisted nematic mode, faster response and smaller operation voltage have been obtained by using a proper amount of chiraldopant and a homeotropically aligning surfactant having an appropriate length of alkyl chains. The characteristics of the HTN cells were strongly dependent on the chain length and the applied bias voltage. It was also found that a chiraldopant played an important role in the director configuration associated with hybrid twisted alignment.
89(2001); http://dx.doi.org/10.1063/1.1352687View Description Hide Description
The spectroscopic properties of and ultraphosphate glasses have been investigated. The concentration quenching rates of in these two systems are lower compared with those in other oxide glasses. The spectral broadening of the measured fluorescence of and 16.67) was observed by increasing temperature. Meanwhile, the lifetime of the level shows the temperature dependence with increasing temperature, ascribed to the possible thermalization of higher-lying sublevels of the level with faster radiative rates and the effect of radiation trapping. At room temperature, the deformation of the emission spectrum line shape has been observed with the increase of concentration due to the reabsorption effect. The 1.5-μm-amplification characteristics of ultraphosphate glasses have been predicted from the calculated gain spectra at different pump powers.