Density control of dressed four-wave mixing and super-fluorescence

For the first time, we study the fluorescence signals induced by spontaneous emission under three different kinds of atom densities (including proper, high, and low atom densities). Apart from the fluorescence signal, we also present the characteristics of images and spectral signals of the probe transmission and four-wave mixing under proper atom density, such as the Autler-Townes splitting of the spectral signals and the images. In addiiton, under other two improper atom densities, we give the observations of spectral signals of two super-fluorescence signals to understand the different contributions of high and low atom densities. The phenomena in spectral signals and images can be well controlled by adjusting the incident beam powers and frequency detunings. Such studies can be used in all-optical controlled spatial signal processing.