Showing papers by "Chenming Hu published in 1977"

Liquid-crystal waveguides for integrated optics

Abstract: Liquid-crystal optical waveguides may be modulated or switched with high sensitivity by electrooptic, magnetooptic or acoustooptic effects. Such guides, however, have relatively slow response times and relatively high scattering losses so that they currently appear limited to special-purpose applications. A review is given on a variety of liquid-crystal optical switches or modulators. Specific work is then described on the analysis and experiment on thin-film nematic liquid-crystal guides with propagation constant controlled by means of an applied voltage across the films. A dynamic scattering switch is also demonstrated. Recent results show switchable grating directions in films having mixtures of nematic and cholesteric liquid crystals. The controlling variable is the frequency of the applied electric field.

Analysis of silicon solar cells with stripe geometry junctions

Abstract: Silicon solar cells with stripe geometry junctions are analyzed. The base region collection efficiency is found to be insensitive to the transmissivity of the electrode and/or the diffused layer but quite sensitive to the width and separation of the stripe junctions. The additional losses of carriers are mainly due to the increased bulk recombination rather than the surface recombination. In one case analyzed the collection efficiency decreases by 22% when the junctions are separated by about one sixth of the diffusion length with the surface recombination velocity at 300 cm/sec. Possible uses of the stripe-junction design in p-n junction cells and Schottky barrier cells are re-examined in the light of the new calculation and found to be less attractive than previously suggested.