Experimental study of suppressing green noise in a diode-pumped intracavity-frequencydoubled laser

Experimental results of green noise suppression in a diode-pumped intracavity-doubled Nd:YAG laser by inserting a QWP between the Nd:YAG rod and mirror, or between the KTP frequency doubler and mirror,and using two cross-doubled crystals are presented. It is shown that the green noise in a folded resonator can be effectively reduced if one of the above methods is used. The introduction of two cross-doubled crystals has reduced the noise by 18％~25%.The experimental results are consistent with theoretical predications.Some problems in the experiment and further improvements are discussed．