Power dependent measurements of the emission bandwidth of a vertical-external-cavity surface-emitting laser driven terahertz source

We investigate the pump-power dependent emission bandwidth of a CW THz emitter which is based on intra-cavity difference frequency generation in a two-color vertical-external-cavity surface-emitting laser. Two Michelson interferometers are employed to investigate the two color laser output and the originating CW THz signal, respectively. This allows a study of the optical modes which contribute to the THz signal. We find that the THz emission bandwidth is strongly depending on the pump power and shows a clear correlation with the number of involved optical modes.