Second Harmonic Generation in Li2B4O7

Second harmonic generation (SHG) has been studied in lithium diborate (Li 2 B 4 O 7 ) single crystal from room temperature up to the melting temperature. The magnitudes of the SHG coefficients d 33 and d 31 , at room temperature are, respectively, 3.1 and 0.4 relative to d 11 of quartz. The decrease of the SHG signal in the high temperature range suggests the possibility of the phase transition to a nonpolar phase.