A Broadband THz-TDS System Based on DSTMS Emitter and LTG InGaAs/InAlAs Photoconductive Antenna Detector.

Ying Zhang,Shaoxian Li,Yanfeng Li,Zhen Tian,Mingxia He,Jianqiang Gu,Chunmei Ouyang,Xiaoling Zhang,Jiaguang Han,Weili Zhang

doi:10.1038/srep26949

Ying Zhang, Shaoxian Li + Show 8 more

Open Access

https://doi.org/10.1038/srep26949

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Journal: Scientific Reports	Publication Date: May 31, 2016
Citations: 36	License type: CC BY 4.0

Affiliation: Tianjin University, Oklahoma State University

Abstract

We demonstrate a 4-f terahertz time-domain spectroscopy (THz-TDS) system using an organic crystal DSTMS as the THz emitter and a low temperature grown (LTG) InGaAs/InAlAs photoconductive antenna as the receiver. The system covers a frequency range from 0.2 up to 8 THz. The influences of the pump laser power, the probe laser power and the azimuthal angle of the DSTMS crystal on the time-domain THz amplitude are experimentally analyzed. The frequency accuracy of the system is verified by measuring two metamaterial samples and a lactose film in this THz-TDS system. The proposed combination of DSTMS emission and PC antenna detection realizes a compact and low-cost THz-TDS scheme with an ultra-broad bandwidth, which may promote the development and the applications of THz-TDS techniques.

Highlights

Besides the consideration on the center frequency and the bandwidth, in recent years, more and more potential applications require optical-fiber-friendly terahertz time-domain spectroscopy (THz-TDS) systems pumped at 1550 nm, where low temperature grown (LTG) InGaAs/ InAlAs based PC antennas and organic crystals such as DAST, DSTMS are used as promising THz sources[19,20,21] and receivers[22,23]
The band coverage of LTG InGaAs/InAlAs based PC antennas can reach up to 5 THz but the center frequency is mainly less than 0.8 THz24–26
We demonstrate a typical free-space 4 f THz-TDS system with a DSTMS crystal as the emitter and a LTG InGaAs/InAlAs PC antenna as the detector, which has a frequency coverage up to 8 THz with a center frequency at 1.44 THz

Summary

Introduction

To realize an optical fiber coupled THz-TDS with a broad bandwidth and a high center frequency, a combination of DSTMS OR emission and LTG InGaAs/InAlAs PC sampling is strongly suggested. This combination is still lack of experimental verification. We demonstrate a typical free-space 4 f THz-TDS system with a DSTMS crystal as the emitter and a LTG InGaAs/InAlAs PC antenna as the detector, which has a frequency coverage up to 8 THz with a center frequency at 1.44 THz. To verify the frequency accuracy of the proposed system, two different metamaterial samples: U-shape split-ring resonators (SRRs) and rectangle hole arrays, as well as a lactose film are tested in the system. The demonstrated system here may pave a new way for the development of ultra-broadband THz systems, promoting the applications of THz-TDS techniques in security check, drug prevention and medical research

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