Dimensions and entropies of chaotic intensity pulsations in a single-mode far-infraredNH3laser

Detailed studies of digitized recordings of periodic and chaotic intensity pulsing of an unidirectional far-infrared ${\mathrm{NH}}_3$ ring laser at 81.5 μm reveal common features of a broad range of different pulsing patterns as well as systematic relationships among entropies, dimensions, and decay rates of the autocorrelation function. Spiral-type ‘‘Lorenz-like’’ chaos of many different spiraling rates and of differing modulation depths has an underlying attractor dimension of 2.0–2.3 and an entropy rate that lies mainly in the range (0.2–0.7)$T^{\mathrm{-}1}$, where T is the average intensity pulsing period. Over a wide range of types of pulsing (spiral chaos, period-doubling chaos, and periodic states) the decay rate of the envelope of the autocorrelation function over short times provides an estimator of the entropy. The results are in excellent agreement with the characteristics of the Lorenz-Haken model for similar operating parameters.