铌酸锂晶体的内偏置场对铁电应用、电光应用和非线性光学应用等均有直接影响。本工作建立了铌酸锂(LN)晶体内偏置场测试方法, 对同成分铌酸锂(CLN)晶体、近化学计量比铌酸锂(nSLN)晶体、掺杂铌酸锂(doped LN)晶体的内偏置场和矫顽场进行测量。结果表明, CLN晶体内偏置场最高(Eint=2.53 kV/mm), nSLN晶体的内偏置场大幅降低, 其中富锂熔体法生长和气相输运平衡(vapor transport equilibration, VTE)法结合得到的nSLN晶体的内偏置场最小, 与CLN晶体相比降低了约两个数量级; 掺杂铌酸锂晶体的内偏置场与CLN晶体相比也普遍降低, 其中掺6.5%(摩尔分数)Mg的CLN晶体的内偏置场约为CLN晶体的四分之一, 掺7%(摩尔分数)Zn的CLN晶体的内偏置场约为CLN晶体的六分之一。最后对组分和掺杂影响内偏置场的因素进行了简要分析。

Internal bias electric field in the lithium niobate (LN) crystal has a direct impact to the ferroelectric, electro-optic, and nonlinear effects of the crystal and the associated applications. A method to measure this field was proposed, and such a measurement in congruent lithium niobate (CLN) crystals, near-stoichiometric lithium niobate (nSLN) crystals, and doped LN crystals was performed. The results show that the internal bias electric field in the CLN crystal (reaching 2.53 kV/mm) is the largest among the three cases. Compared with the CLN crystal, this field greatly reduces in the nSLN crystals, and can be even lower by two orders of magnitudes for those grown by the lithium-rich melts method followed by vapor transport equilibration (VTE) treatment. In the doped LN crystals, the internal bias electric fields for the cases of 6.5% (mole fraction) Mg and 7% (mole fraction) Zn doping are 4 and 6 times smaller than that in the CLN crystal, respectively. The reason for causing the difference in the two doped cases was briefly discussed.