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Abstract
The conditions for generating low frequency electrical and optical oscillations in a liquid crystal cell-photoresistor system with a frequency dependent electrooptical feedback are treated theoretically and verified experimentally. The equivalent circuit of the system may be represented by three RC groups. There is in this configuration a frequency where the phase shift will be η, and suitable condition for oscillations will arise. The equivalent circuit of the liquid crystal cell is considered and differential equations characterizing the transition are derived when applying a single rectangular pulse. A comparison between the theoretical and the experimentally plotted transient characteristics is made. The differential equation constants are determined from the experimentally obtained plots using the least squares method. The quasiresonance frequency of the liquid crystal cell is given by the solution of the differential equation. The obtained experimental data verifies the theoretical predictions.