Microphotonics

de K. Asakawa, Edwin L. Thomas

"The objective of this thesis is to investigate the electrooptical properties of a dipole suspension. A dipole suspension consists of needle-like crystals which, in the presence of an electric field, orient themselves parallel to it. If the dipoles align themselves parallel to incident light, the suspension will transmit the light. If no electric field is present, the dipoles are in a random state, and little light is transmitted. The projected area of the dipoles is smaller when they are in the aligned state. Commercially, a dipole suspension is available from Marks Polarized Corporation as the product Varad. This thesis will investigate the following properties of the dipole suspension Varad: 1) spectral characteristics 2) off-axis properties 3) rise and fall times 4) the dependence of optical density on the voltage and frequency of the electric field Statistically designed experiments were used to investigate the above factors.^ A spectrophotometer was used to investigate the spectral characteristics, with the wavelength, frequency, voltage, and angle of incident light being varied. For the time studies, a dual beam scope was used to monitor the voltage to the dipole suspension and the transmittance simultaneously. Photographs made from the oscilloscope were used to determine the rise and fall times of the Varad. All the data was analysed using statistical regression techniques, but it was not possible to find a model for all the data. The regression models that v/ere found are shown below, along with a short discussion of each. 1) ln(D - 0.6) = 0.9121 - 0.0059 E, where E = the electric field intensity Density changes exponentially as the voltage is increased. 2) ln(D - D0) = 0.1626 - 0.0021 f, where f = frequency (Hz) D0 = minimum density obtained A change in frequency causes the density to change exponentially also, but to a lesser degree than voltage.^ 3) D = 0.4468 + 1.524/cos(w), where w = angle of incidence in degrees As the angle of incidence is increased, the density increases, but the cosine law does not fully account for the changes observed. 4) ln(T - T0) = b0 + b1 E, where T = fall (milliseconds) T0 = minimum fall time b0, b1 are constants Voltage has a very significant effect on both rise and fall times. The higher the voltage the shorter the rise and fall times. Frequency has very little effectt on the rise and fall times, but the effect is large enough to change the estimates of the coefficients b0 and b1. The spectral characteristics could not be fit to a mode because of the complicated relationships that existed. Its nonneutrality makes Varad very questionnable for use in the photographic field."--Abstract.