Abstract
Many time-domain terahertz applications require systems with high bandwidth, high signal-to-noise ratio and fast measurement speed. In this paper we present a terahertz time-domain spectrometer based on 1550 nm fiber laser technology and InGaAs photoconductive switches. The delay stage offers both a high scanning speed of up to 60 traces / s and a flexible adjustment of the measurement range from 15 ps – 200 ps. Owing to a precise reconstruction of the time axis, the system achieves a high dynamic range: a single pulse trace of 50 ps is acquired in only 44 ms, and transformed into a spectrum with a peak dynamic range of 60 dB. With 1000 averages, the dynamic range increases to 90 dB and the measurement time still remains well below one minute. We demonstrate the suitability of the system for spectroscopic measurements and terahertz imaging.
Highlights
Terahertz waves feature unique properties: like microwaves, terahertz radiation passes through a plethora of non-conducting materials, including paper, cardboard, plastics, wood, ceramics and glass-fiber composites [1]
In this paper we present a compact fiber-coupled THz-TDS system based on 1.5 μm fiber laser technology and InGaAs/InAlAs photoconductive switches
Due to a precise reconstruction of the time axis, the system drastically reduces the effect of jitter noise and achieves a high dynamic range in conjunction with broad bandwidth and fast measurement speed
Summary
Terahertz waves feature unique properties: like microwaves, terahertz radiation passes through a plethora of non-conducting materials, including paper, cardboard, plastics, wood, ceramics and glass-fiber composites [1]. Terahertz spectrometers operating at 1.5 μm take full advantage of mature and costefficient telecom components and are well suited for real-world applications [14]. These advances notwithstanding, state-of-the-art THz-TDS systems usually achieve the targeted signal-to-noise (SNR) ratios via time-consuming signal averaging methods, which is no hurdle if the quality of the signal is more important than the measurement speed. In this paper we present a compact fiber-coupled THz-TDS system based on 1.5 μm fiber laser technology and InGaAs/InAlAs photoconductive switches. Due to a precise reconstruction of the time axis, the system drastically reduces the effect of jitter noise and achieves a high dynamic range in conjunction with broad bandwidth and fast measurement speed. We conclude with application examples in the fields of spectroscopy and imaging
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