半導体微小機械共振器中のモード間結合効果の解明と超高感度テラヘルツ波検出への応用

本研究旨在探讨微机电梁式谐振器中的模式耦合效应，并探讨其在高灵敏度太赫兹传感中的应用。在今年的研究中，我们继续通过测量热调制模式耦合强度来研究模式耦合效应的物理起源，模式耦合强度由耦合的高频模式与低模同时激发时的谐振频率偏移决定。当输入热量被施加到MEMS梁时，MEMS梁被加热到屈曲条件，这改变了模式耦合强度以及MEMS梁的机械非线性。我们发现，模式耦合强度的变化与机械非线性的变化趋势非常相似，表明这两种效应可能有着相同的起源。此外，我们还证明了机械非线性主要来自于机械振动过程中的梁的伸长，并可以通过梁的内部应变来控制。这已经通过在MEMS梁中输入热量或引入晶格失配来验证。这些结果对于理解MEMS梁谐振器的基本物理特性非常有用，因此对于设计高灵敏度的MEMS探测器是有用的。

The objective of this study is to clarify the mode coupling effect in MEMS beam resonators and explore its possible application in high sensitivity terahertz sensing. In the research of this year, we continued investigating the physical origin of the mode coupling effect by measuring the thermally modulated mode coupling strength.The mode coupling strength is determined by the resonance frequency shift when the coupled high frequency mode is excited simultaneously with the lower mode. As an input heat is applied to the MEMS beam, the MEMS beam is heated up to the buckling condition, which changes the mode coupling strength, as well as the mechanical nonlinearity of the MEMS beam. We have found that the mode coupling strength change has a very similar trend with the mechanical nonlinearity, indicating that these two effects may have the same origin. In addition, we have demonstrated that the mechanical nonlinearity mainly comes from the extended beam length during the mechanical oscillation, and can be controlled by the internal strain in the beam. This has been verified by inputting heat or introducing lattice mismatch in the MEMS beam. These results are very useful for understanding the fundamental physics in MEMS beam resonators, and hence are useful for designing highly sensitive MEMS detectors.