Abstract
The fast detection of terahertz radiation is of great importance for various applications such as fast imaging, high speed communications, and spectroscopy. Most commercial products capable of sensitively responding the terahertz radiation are thermal detectors, i.e., pyroelectric sensors and bolometers. This class of terahertz detectors is normally characterized by low modulation frequency (dozens or hundreds of Hz). Here we demonstrate the first fast semiconductor-based terahertz quantum well photodetectors by carefully designing the device structure and microwave transmission line for high frequency signal extraction. Modulation response bandwidth of gigahertz level is obtained. As an example, the 6.2-GHz modulated terahertz light emitted from a Fabry-Pérot terahertz quantum cascade laser is successfully detected using the fast terahertz quantum well photodetector. In addition to the fast terahertz detection, the technique presented in this work can also be used for optically characterizing the frequency stability of terahertz quantum cascade lasers, heterodyne detections and photomixing applications.
Highlights
The terahertz wave[1] with the frequency defined between 0.1 and 10 THz is of great interest due to its unique properties such as transparency for papers and plastic materials, abundant absorption “fingerprints” of various chemicals, and potential large communication bandwidth
In this work by utilizing a carefully designed microwave transmission line to efficiently extract the radio frequency (RF) signal, we first demonstrate the fast detection of GHz-modulated terahertz radiation using a terahertz quantum well photodectors (QWPs) with a device area of 400 × 400 μm[2]
As a proof for the fast detection, a 6.2-GHz modulated terahertz light emitted from a long cavity terahertz QCL was successfully detected in terms of inter-mode optical beat note spectrum using the fast terahertz QWP
Summary
The terahertz wave[1] with the frequency defined between 0.1 and 10 THz is of great interest due to its unique properties such as transparency for papers and plastic materials, abundant absorption “fingerprints” of various chemicals, and potential large communication bandwidth. The fast terahertz detector is the last component for implementing fast terahertz applications since the terahertz source employing the quantum cascade design has been already verified for being fast modulated upto 35 GHz14. In the mid-infrared wavelength range, room temperature high frequency heterodyne detection upto 110 GHz with small mesa quantum well infrared photodetectors has been already demonstrated in 2006 employing the air bridge technique and coplanar waveguide configuration[17]. In this work by utilizing a carefully designed microwave transmission line to efficiently extract the radio frequency (RF) signal, we first demonstrate the fast detection of GHz-modulated terahertz radiation using a terahertz QWP with a device area of 400 × 400 μm[2]. As a proof for the fast detection, a 6.2-GHz modulated terahertz light emitted from a long cavity terahertz QCL was successfully detected in terms of inter-mode optical beat note spectrum using the fast terahertz QWP
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