A single-mode class B laser with monochromatic external optical injection is described by Sebastian Wieczorek, Bernd Kraupskopf & Daan Lenstra .
The governing equations are
where B is the rescaled cavity lifetime of photons, F is the rescaled damping rate of the relaxation oscillations and K is the dimensionless injected field strength. Variables x and y are the components of the electric field E inside the laser and z is the normalized population inversion. For parameter values With parameter values K=0.3, , , B=0.015 and , it produces a toroidal structure (Fig. 1) whose Kaplan-Yorke dimension is 2.76.
A simpler set of equations capturing most of the dynamical characteristics of the previous system was proposed by Konstantinos Chlouverakis & Julian Sprott 
With parameter values K=0.4, and , it produces a toroidal chaotic attractor (Figs. 2) whose Kaplan-Yorke dimension is 2.54.
 S.Wieczorek, B. Krauskopf & D. Lenstra, A unifying view of bifurcations in a semiconductor laser subject to optical injection, Optics Communications, 172, 279295, 1999.
 K. E. Chlouverakis & J. C. Sprott, A comparison of correlation and Lyapunov dimensions, Physica D, 200, 156-164, 2004.