Experimental observations and computer simulations of locked states in an infinite-dimensional periodically Q-modulated NMR laser with feedback are presented. Arnold tongues (AT’s) were observed both for a harmonic and an anharmonic (square-wave) modulation. The width of selected AT’s were significantly larger for the anharmonic modulation than for the harmonic modulation. In addition, the AT’s were observed to split into regimes of locking to different fundamental limit cycles as the modulation amplitude was increased. Significant deviations of the locking behavior from predictions of the one-dimensional circle map were observed. The experimental results agreed in an excellent way with simulations with a phenomenological Bloch-Kirchhoff model with a heuristic relaxation term and consequently present an exemplary test for the model.

• Received 13 June 1994

DOI:https://doi.org/10.1103/PhysRevE.50.3383