Abstract

Amplified spontaneous emission (ASE) signals have been analyzed using an algorithm which computes the dimension of the underlying dynamical attractor if it exists. Experimental time series were obtained by digitizing the detected output of a linearly polarized component of a heavily saturated, homogeneously broadened Xe-He (3.51-μm) discharge tube. The autocorrelation time, τ, of the ASE signal was ~20 ns in accord with Fourier transform limits. The time between two consecutive data points was changed from ~0.02τ to ~0.5τ. There was an apparent dimension of low value for short interpoint time intervals which is likely due to a combination of the transient autocorrelations and the limited data record (1023 pts.). For longer time intervals no dimension could be found, a result similar to that for random noise. We conclude that the signals show no evidence of a dynamical cause for the fluctuations or, if it exists, the dimension of the underlying attractor was not discernible (at least greater than eight) even when the analysis was carried out in reconstructed phase spaces of dimensions up to twenty. This type of noisy behavior contrasts sharply with the low dimensional chaotic output of the unstable lasers even though they may have similar power spectra.

© 1985 Optical Society of America