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Characteristics and Performance of KNbO3-YAlG/Nd Intracavity Second Harmonic Generation

The intracavity second harmonic generation of YAlG/Nd laser using KNbO3 single crystal was demonstrated and it was compared with that using Ba2NaNb5O15 crystal. KNbO3 was found to be suitable for this application because of (1) its large conversion efficiency, i.e. (d2/n3)KNbO3 =0.8±0.1(d2/n3)Ba2NaNb5O15 , (2) its resistance to damage by intense green light output, and (3) its very low optical loss coefficients at the fundamental and the harmonic wavelengths (about 0.25%/cm at 1.06 µm). About 90% conversion of the optical second harmonics was obtained The thermal conductivity of KNbO3 was found to be larger than that of Ba2NaNb5O15 due to the increasing crystal temperature caused by the internal laser power.