1,721,017 research outputs found
A grey scale ssflc display and its matrix addressing”, 4, Proceedings of the 29th Freiburg Workshop on Liquid Crystals, Friburgo (D), 22-24 marzo 2000
No full textLightwave circuits based on organic materials for optical signal filtering and switching in WDM communication systems
No full textPeriodic structures are suitable to make wavelength selective photonic devices for a large variety of applications ranging from fiber optic communications, biosensors, and lasers. We present our experimental and simulation results on guided wave devices, which can be switched and tuned electrically and optically by light driving signals in micro-and nanostructured device geometries.
Wavelength selectivity is obtained by using either the phenomenon known as whispering gallery modes in microsphere resonator or Bragg diffraction. In both cases we consider organic materials as medium to tune spectral response of the proposed devices
Tolerant SSFLC matrix display addressing with equal selection and data voltages
No full textThis paper describes novel addressing waveforms featuring the widest operation at the lowest possible total voltage for a mechanism based on the dielectric torques existing in the SSFLC cell in addiction to the polarization torques, as found by simulations and experiments with chevron cells. The operation at the lowest voltage end of the Compensated Rome modes has been improved and equal selection and data voltages are here used allowing hf stabilization with reduced power supply. Simple adjustments in the selection waveforms provide operation at least in range of temperature 20 °C to 30 °C for fixed 20 V and 30 [mu]s addressing with a commercial FLC mixture
Modi di indirizzamento matriciale per display a cristalli liquidi ferroelettrici
No full textA simple model of ferroelectric liquid crystal cells is discussed. By means of two compute programs three different classes of addressing modes have been found. The "high voltage" new "Rome" and "Rome compensated" addressing modes have been used to drive our analog grey scale SSFLC display
Polarization properties of near-infrared light confined in nematic liquid crystal channel waveguides embedded in SiO2/Si grooves
No full textLinear and non-linear optical properties[1] of liquid crystals (LC) make them extremely
appealing for use in a wide range of different optoelectronic applications other than displays.
Their high optical anisotropy (in some cases higher than 0.2) implies large phase shifts in
very short optical paths. Furthermore, their strong electro-optic effect allows rapid
reorientation of their optical axis with indeed very low voltages in the range of only a few volt
and hence compatible with current silicon technology. In particular, this last property makes
them very attractive for low power consumption photonic applications.
In this communication, light polarization dependence of channel waveguides made of SiO2/Si
grooves filled with the commercial nematic liquid crystal E7 is shown. Grooves were
obtained by initially wet etching phosphorous-doped (1 0 0) silicon substrates and then by
thermally growing SiO2 up to a thickness of about 2 μm[2]. The cross section of the groove
resulted with this method was of trapezoidal shape due to the preferential etching plane of
silicon at 54.7° with respect to the wafer plane. The upper width of the groove as defined
from the lithographic mask was 10 μm. The processed silicon substrate was subsequently
assembled into a typical LC cell with a sodalime glass plate on the top. The inner surface of
the glass had been previously spin-coated with Nylon 6, which was then rubbed for the
alignment of the LC molecules approximately along the grooves. Propagation of infrared laser
light (1550 nm) launched at one end of the waveguide by butt coupling was observed for a
channel length of 2 cm. The signal at the output of the waveguide could be also coupled to a
second optical fiber. The guided light showed a good optical confinement both in theory and
the experiment. The simulated output profile by means of a typical beam propagation method
was found to be very similar to the one grabbed at the output of the waveguide. Furthermore,
the experimentally observed polarisation dependence of the light confinement into the
waveguide was correctly predicted from our model. In particular, near infrared input light was
controlled by using a fiber pigtailed sequence of 1/4wave-1/2wave-1/4wave plates. A
measurement of light intensity versus the angle of input light polarization will be also
reported. Such measurement shows that the orthogonal polarization state, for which the
optical electric field “sees” only the lower LC refractive index (ordinary), was suppressed by
more than 20 dB. This was justified by the observed pre-tilt angle of the molecules with
respect to the propagation direction along the channel
Ferroelectric LCD low voltage matrix addressing technique
No full textWe developed new addressing modes in which ic drivers powered with low voltages can provide short line addressing times. Time-overlapping selection waveforms and techniques for reducing crosstalk and improving operating range were incorporated. 230 microsecond single-shot writing at room temperature with 8.8 V supply voltage is reported, together with measurements of sticking effects and operating ranges
Guida d'onda ottica non lineare a cristallo liquido su silicio
No full textThe optical nonlinear transmission of a channel waveguide with E7 liquid crystal core infiltrated in a SiO2/Si V-groove is experimentally and theoretically investigated. Low input
power excites optical nonlinearity due to optically induced reorientational effect
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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