ENCODING AND DECODING MESSAGES WITH CHAOTIC LASERS

We investigate the structure of the strange attractor of a chaotic los s-modulated solid-state laser utilizing return maps based on a combina tion of intensity maxima and interspike intervals, as opposed to those utilizing Poincare sections defined by the intensity maxima of the la ser ((I) OVER DOT = 0, (I) DOUBLE OVER DOT < 0) alone. We find both ex perimentally and numerically that a simple, intrinsic relationship exi sts between an intensity maximum and the pair of preceding and succeed ing interspike intervals. In addition, we numerically investigate enco ding messages on the output of a chaotic transmitter laser and its sub sequent decoding by a similar receiver laser. By exploiting the relati onship between the intensity maxima and the interspike intervals, we d emonstrate that the method utilized to encode the message is vital to the system's ability to hide the signal from unwanted deciphering. In this work alternative methods are studied in order to encode messages by modulating the magnitude of pumping of the transmitter laser and al so by driving its loss modulation with more than one frequency.