Coupled microcavity resonators can change the input wavelength by changing the parameter of resonators; can control the propagation of slow light or fast light in room temperature, so there is potential advantage in practical application to create slow light and fast light by using c.

In the authors' points,the main developing trends and research frontier in this field should be focused on the followingfour directions, first, high-power and large-energy laser crystals; second, practical mid-infraredlaser crystals; third, laser crystals emitting at UV and visible regions; fourth, ultrafast laser gainand amplifier media suitable for LD pumping.

Basing on both the spectra analysis of ultrafast lasers and the speckle statistical theory,we derive the autocorrelation function of ultrafast dynamic speckle intensity.