Controlling chaotic systems with occasional proportional feedback

Utilizing the chaos control technique of occasional proportional feedback (OPF), we designed and constructed an inexpensive and easy to assemble electronic OPF controller. A number of built-in features provide ample versatility to enable the controller to be used with a wide variety of chaotic experimental systems. The controller has a standard OPF correction signal output, but also allows for the addition of a modulated signal to the correction. The rate and active duration of the correction pulse, the offset voltage, and the effective window width are variable. We present the basic principles of OPF control and discuss the individual component functions of the OPF controller. We have successfully used this controller to stabilize chaotic fluctuations in the frequency emission from a tunable lead–salt stripe geometry infrared diode laser.