The results measured with Z Scan technique show that the cluster exhibits a self focusing property, and the excited state absorption is the main mechanism of the optical limiting effect of the metal cluster compound.

By theoretic analyzing the energy level structure of the color center and calculating the saturable optical intensity of the excited state absorption, the authors point out the possibility of realizing passive mode-locking by using LiF crystal with the relaxation time of the ground state in nanosecond magnitude.

The change of the small signal gain for a Cr:LiSAF laser is calculated with the change of pump power on consideration of the excited state absorption and upconversion process,and the influence of the temperature inside Cr:LiSAF on the small signal gain is analyzed.

The optical limiting effect of [Ag(L4)(NO_3)·H_2O]_n is stronger for ps than that of [Ag(L4)(NO_3)·H_2O]_n for ns, and the excited-state absorption is the main mechanism of the optical limiting effect of the coordination polymers.

The optical limiting effect of the coordination polymers [Cd(L4)(SO4)(H2O)2]n originate mainly from the excited-state absorption.

In this thesis, the mechanism of excited-state absorption-enhanced transient thermal refraction (excited-state thermal refraction, ESTR) in cluster and organic materials’solution media was investigated.

Based on the energy level diagram, the rate equations indicate that ASE and ESA eliminate the population of upper energy level, make slope efficiency of 1 444 nm lasers lower and reduce gain.

The ground and excited state absorption cross sections of the Cr~(4+):YAG saturable absorber at the ~4 F(3/2)-~4 I(9/2) transition wavelengths of Nd~(3+) were measured by a pump-probe method.