Fabrication of photoconductive antenna with mesa structure for terahertz spectroscopy

太赫兹(THz)电磁波的频率为10^12赫兹，波长为100微米。太赫兹波用于太赫兹时域光谱(THz-TDS)装置中，用于材料和化合物的非破坏性、非侵入性表征。研究表明，包括有机材料、炸药、药物化合物和生物制剂在内的许多材料在太赫兹频率上都有明显的特征。在这方面，太赫兹时域成像(THz-TDI)和光谱学(THz-TDS)不仅引起了科学家的极大兴趣，而且也引起了工业利益相关者的极大兴趣，因为它们在化学传感、医学诊断和无损质量控制方面具有独特的能力。THz-TDS和THz-TDI系统的潜在应用和范围在很大程度上取决于基于光导天线(PCA)器件的THz发射机和接收机。以发射机为例，目前最先进的发射机PCA和PCA阵列利用短载流子寿命半导体衬底产生超快电流，在飞秒激光泵浦下产生宽带太赫兹辐射。 在这个项目中，我们将设计、制造和表征三维台面状太赫兹主元分析，它比普通平面主元分析具有更高的效率。PCA将被整合到支持公司的产品中，该产品测量塑料容器的单层厚度。高性能主成分分析将能够测量更厚或更多的吸收层，以及具有更多层的容器。此外，MESA PCA将工作在激励激光的通信波长(@1550 nm)，因此可以利用光纤耦合来提供灵活和紧凑的太赫兹系统。

Terahertz (THz) electromagnetic waves have frequencies of order 10^12 Hz and wavelengths order 100 um. THz waves are used in THz time domain spectroscopy (THZ-TDS) setups for non-destructive, non-invasive characterization of materials and compounds. It has been shown that many materials including organic materials, explosives, pharmaceutical compounds, and biological agents have distinct signatures in the terahertz frequencies. In this regard, terahertz time-domain imaging (THZ-TDI) and spectroscopy (THZ-TDS) are of great interest not only to scientists but also to industrial stake holders for their unique capabilities in chemical sensing, medical diagnosis, and non-destructive quality control. The potential application and scope of THz-TDS & THZ-TDI systems are largely determined by the THz transmitter and receiver that are both based on photoconductive antenna (PCA) device. Taking the transmitter as an example, state of the art transmitter PCAs and PCA arrays utilize short carrier lifetime semiconductor substrate to generate ultrafast current to produce broadband THz radiation under a femtosecond optical laser pump. In this project we will design, fabricate and characterize three-dimensional mesa-like terahertz PCA that offers higher efficiency than the common planar PCA. The PCA will be integrated into the supporting company's product that measures the individual layer thickness of plastic containers. High performance PCA will enable the measurement of thicker or more absorbing layers, as well as containers having more layers. Moreover, the mesa PCA will work at the telecommunication wavelength (@1550 nm) for the excitation laser, and thus fiber-coupling can be utilized to give an agile and compact THz system.