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

本研究的目的是阐明MEMS光束谐振器中的模式耦合效应，并探索其在高灵敏度太赫兹传感中的可能应用。在今年的研究中，我们继续通过测量热调制模的耦合强度来研究模耦合效应的物理来源，模式耦合强度是由耦合的高频模与低模同时激励时的共振频率漂移决定的。当输入热量施加到MEMS梁上时，MEMS梁被加热到屈曲状态，从而改变了MEMS梁的模式耦合强度和力学非线性。我们发现，模式耦合强度的变化与力学非线性的变化趋势非常相似，这表明这两种效应可能具有相同的起源。此外，我们还证明了机械振动过程中的机械非线性主要来自延长的梁长，并且可以由梁的内部应变来控制。通过在MEMS光束中输入热量或引入晶格失配来验证这一点。这些结果对于理解MEMS光束谐振器的基本物理是非常有用的，因此对于设计高灵敏度的MEMS探测器也是有用的。

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.