Relaxation oscillations and stability

The phenomenon of relaxation oscillations is reexamined from the viewpoint of stability theory. We show that undamped relaxation oscillations with modulation depths of unity can be understood as centers at zero photon density. In addition, we show that the threshold pump rate and the criteria for eliminating relaxation oscillations can be obtained from the stable node conditions at the nonzero photon density critical point. Experimental results for the 496 μm optically pumped CH
3
F laser are discussed.