Blue SHG characteristics and homogeneity of the TSSG grown potassium lithium niobate (KLN) crystal with high Li2O content

Abstract

The high quality and crack-free KLN crystal with high Li2O content has been grown along the 〈110〉 axis by the TSSG method from the melt of 31mol% K2O, 26mol% Li2O and 43mol% Nb2O5. The size of the as-grown KLN crystal is about 6×9×29mm3. The XRD analysis gives the lattice constant a=12.583Å, and c=4.041Å near the c value of the stoichiometric KLN. The Curie temperature of this crystal is determined to be 540°C by the dielectric constant measurement. The blue SHG characteristics of the KLN crystal are investigated by using a 3900S Ti: sapphire CW tunable laser. The FWHMs of the wavelength- and temperature-tuning curves for the NCPM SHG are determined to be 0.4nm and 1.2°C, respectively. The blue laser light with 1.45mW output at 416.7nm is achieved at room temperature by the single-pass SHG for 903mW input power. The blue SHG conversion efficiency is estimated to be 0.25%/W that is the highest value obtained up to now. The temperature-tuned blue laser light with continuous output from 416.7 to 423.5nm is obtained by increasing the crystal temperature from 23.5°C to 80°C. The temperature coefficient of the NCPM wavelength is 0.295nm/°C. The investigated KLN crystal, especially its middle part, has a good homogeneity of the room temperature NCPM wavelength along the growth axis (<2nm).