The infrared transmission spectrum of potassium lithium niobate crystal was studied.The result showed that the spectrum properties of the crystal grown from the melt with higher Li

2

O contents is better than those of the crystal grown from the melt with lower Li

2

O contents

the latter has an absorption peak at the wavelength of 480urn while the former has not

so when a laser beam pass across the crystal

the optical loss for the former is lower than that for the latter.The reasons for the result are related to the reduction of replace chance of Nb atom at Li atom site in potassium lithium niobate crystal grown from melt with higher Li

2

O contents.The reduction of optical loss is very beneficial to the increasing of the second harmonic generation efficiency of the crystal.The second harmonic generation properties of potassium lithium niobate crystal were studied.It showed that the potassium lithium niobate crystal has no frequency-doubling performance unless it has necessary Li contents.The second harmonic generation properties will be improved as the Li contents in the crystal increases.The blue-green laser have been obtained by doubling quasi CW-Ti: sapphire near infrared laser in the wavelength range of 890~960um using potassium lithium crystal grown from the melt with Li

2

O 26mol%

the results showed that the crystal sample has good frequency-doubling efficiency.The means of enhancing the second harmonic generation efficiency of potassium lithium niobate crystal were discussed.It is deduced that the second harmonic generation efficiency will be increased while the light loss of the potassium lithium niobate crystal reduces.