Fundamental studies on semiconductor coupled multilayer cavity for novel planar-type terahertz emission devices

半导体耦合多层腔中两个腔模的差频产生（DFG）是一种新型的平面型太赫兹辐射器件。在这项研究中，我们开发了基于GaAs/AlAs多层结构的耦合多层腔的设计和制造的基础技术，并通过使用飞秒激光脉冲测量各种类型的混频信号来证明其作为太赫兹光源的有用性。研究发现，耦合腔结构内部的非线性极化率反转是实现太赫兹强差频的关键技术之一。通过直接键合在高折射率衬底上生长的两个外延薄膜，成功地引入了磁化率反转。由于反转的信号增强，清楚地观察到在模拟和实验测量的太赫兹波形使用飞秒激光脉冲。

Difference-frequency generation (DFG) of two cavity modes in a semiconductor coupled multilayer cavity is a new concept for compact and useful planar-type terahertz emission devices. In this study, we developed fundamental technologies for design and fabrication of the coupled multilayer cavity based on GaAs/AlAs multilayer structures and demonstrated its usefulness as a terahertz light source by measuring various types of frequency-mixing signals using femtosecond laser pulses. We found that the nonlinear susceptibility inversion inside the coupled cavity structure is one of the most important technologies for strong DFG in the terahertz region. The susceptibility inversion was successfully introduced by direct wafer-bonding of two epitaxial films grown on high-index substrates. Signal enhancement due to the inversion was clearly observed in both simulated and experimentally measured terahertz waveforms using femtosecond laser pulses.