IEEE Trans Ultrason Ferroelectr Freq Control. 2017 Sep;64(9):1361-1367. doi: 10.1109/TUFFC.2017.2702579. Epub 2017 May 9.
Nonlinear generation of harmonics is measured on the wafer level on temperature compensated surface-acoustic-wave resonators on lithium niobate. The second-harmonic response features strong peaks looking like multiple resonant modes. The product of the frequency difference between the successive peaks to the substrate thickness is found to remain almost constant. The results also show that the level of the harmonic signal strongly depends on the roughness of the back side of the substrate. Due to these findings, it was assumed that the signal is due to nonlinear generation of a bulk mode. This assumption is confirmed experimentally by measuring the second-harmonic wave field on the back side of the substrate with an interferometer. Possible nonlinear mechanisms explaining these results are discussed.
在铌酸锂温度补偿声表面波谐振器的晶圆级上测量了谐波的非线性产生。二次谐波响应具有很强的峰，看起来像多个共振模式。发现连续峰之间的频率差与衬底厚度的乘积几乎保持不变。结果还表明，谐波信号的强度强烈依赖于衬底背面的粗糙度。由于这些发现，人们认为该信号是由于体模的非线性产生。通过使用干涉仪在衬底背面测量二次谐波场，实验证实了这一假设。讨论了解释这些结果的可能的非线性机制。
