Interacting pairs of periodic solutions lead to tori in lasers subject to delayed feedback

Models of class-B lasers subject to either an optoelectronic or an optical feedback are investigated analytically and numerically. We derive slow time amplitude equations from the laser delay differential equations and find multiple bifurcating and isolated branches of periodic solutions. We then show that secondary bifurcations to tori result from the interaction of pairs of Hopf bifurcations. The branches emerging from these bifurcations are followed numerically using a continuation method developed for delay differential equations.