Abstract-A terahertz EO detector with large dynamical range, high modulation depth and signal-noise ratio

• Xinjian Pan^a, b, 
• Yi Cai, , 
• Xuanke Zeng^a, b, 
• Shuiqin Zheng^a, b, 
• Jingzhen Li^a, 
• Shixiang Xu^a, , 

• ^a Shenzhen Key Lab of Micro-Nano Photonic Information Technology, College of Electronic Science and Technology, Shenzhen University, Shenzhen, Guangdong 518060, PR China
• ^b SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Guangdong 518060, PR China
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• http://www.sciencedirect.com/science/article/pii/S0030401817300317
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• The paper presents a novel design for terahertz (THz) free-space time domain electro-optic (EO) detection where the static birefringent phases of the two balanced arms are set close to zero but opposite to each other. Our theoretical and numerical analyses show this design has much stronger ability to cancel the optical background noise than both THz ellipsometer and traditional crossed polarizer geometry (CPG). Its optical modulation depth is about twice as high as that of traditional CPG, but about ten times as high as that of THz ellipsometer. As for the dynamical range, our improved design is comparable to the THz ellipsometer but obviously larger than the traditional CPG. Some experiments for comparing our improved CPG with traditional CPG agree well with the corresponding theoretical predictions. Our experiments also show that the splitting ratio of the used non-polarization beam splitter is critical for the performance of our design.