Dynamic behavior and chaos in bistable opticaldevices

Abstract

This thesis work consists of two parts : one is the instability and chaos in a liquid crystal bistable optical device (BOD), and the other the bistability and chaotic behavior in a driven nonlinear oscillator using an optical device, LED. In the first part of this work, a hybrid bistable optical device is realized by using a simple liquid crystal light modulator based on the dynamic scattering. Regenerative oscillation and monostable pulse generation have also been demonstrated to study its transient behavior in this BOD by applying a negative feedback with a capacitor-resistor circuit. Next, a liquid crystal BOD with a delayed feedback is employed to study the chaotic behavior. In this BOD the periodic windows are observed for the first time. A number of periodic windows. i.e., 3, 4, 5, and 7T (T means a period), have been easily observed as well as period doublings up to 4T and chaos. Isomers and even harmonies in a periodic window are also observed for the first time. Two 4T 3-rd harmonic isomers and a 3T 4-th harmonic have been observed as well as a 2T 3-rd harmonic. Computer simulations based on a difference and a delay-differential equation with a trapezoid function show good agreement with the experiment. In the second part of this work, an LED is used with a resistor and an inductor to build a driven nonlinear oscillator, and thereby to realize an optical source displaying significant bistability at small driving voltage and a sequence of chaotic scenarios at higher driving voltage. To explain the bistability, the oscillator is modeled and analyzed as anharmonic oscillator. To understand the qualitative features of each chaotic scenario in the sequence, that starts with a corresponding fundamental period (1, 2, 3, 4, and 5), we plotted bifurcation diagrams and return maps and then observed the evolution of return maps as driving voltage. Crisis and intermittency are also observed. Computer simulations based on the modified Rollins-Hunt model and a SPICE...