Abstract

Experimental and theoretical investigations of a multimode standing-wave cw dye laser have been carried out. For a three-mirror cavity the laser spectrum is found to evolve by discrete transitions, with increasing pump power, between spectra composed of three stable modes to spectra composed of many modes whose amplitudes fluctuate strongly. At low powers there are three stable modes, separated by 2 GHz (8 cavity mode spacings). When the pump power is raised, the separation suddenly jumps to 4 GHz. After a range of power in which the spectrum is unstable, three stable modes again appear, now with a spacing of 8 GHz. A further increase of pump power leads eventually to a quasicontinuous spectrum, with a spectral width corresponding to about 100 cavity mode spacings. The behavior at low powers is caused by the simultaneous presence of spatial hole burning and an extremely weak etalon which arises spuriously from diffuse backscatter from the folding mirror. In a regime corresponding to unstable spectra, we find experimental evidence for deterministic chaos. We also have carried out numerical simulations of this type of laser using realistic parameters and find qualitative agreement with experiment, including the decrease of mode-intensity correlation time with increasing pump Power.

© 1987 Optical Society of America