Terahertz single photon detectors

Abstract

<p indent="0mm">Terahertz detection plays an increasingly important role in various fields, such as astronomy, national defense, security checking, and biotechnology. With the development of technology, the sensitivity of terahertz detectors is continuously improving, and the detection of terahertz single photons has been demonstrated in recent years. In the terahertz band, owing to the low photon energy of terahertz photons and serious transmission losses in the atmosphere, research and development on terahertz single-photon detectors have faced significant technical challenges. In this article, we first introduce the operating mechanisms, main performance indicators, and measurement systems for terahertz single-photon detectors and identify the basic requirements for realizing terahertz single-photon detection. We then introduce several terahertz single-photon detectors, including semiconductor quantum dot, semiconductor quantum well, and superconducting quantum capacitance detectors. The history of the development, operating mechanisms, and key indicators of these terahertz single-photon detectors is also summarized. Noise equivalent power of the order of 10⁻²¹ W/Hz^1/2 has been achieved using semiconductor quantum dot and quantum well detectors. Although both these have a large current response and dynamic range, their quantum efficiency is low. Superconducting quantum capacitance detectors have achieved single-photon detection at <sc>1.5 THz</sc> with a noise equivalent power better than 10⁻²⁰ W/Hz^1/2 and detection efficiency up to 90%. In addition, some terahertz detectors such as nanobolometers have shown potential for terahertz single-photon detection, and we introduce the operating mechanism and development status of these devices as well. We also analyze the prospects of terahertz single-photon detectors for applications in terahertz imaging, astronomical observations, and quantum information technology, highlighting some major international research projects and reported examples of such applications. We further summarize the advantages of terahertz single-photon detectors for these applications. Finally, we review the performance of terahertz single-photon detectors and discuss future development trends.