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Proceedings Paper

Development of THz light sources based on QCL technology
Author(s): Kazuue Fujita; Akio Ito; Masahiro Hitaka; Tatsuo Dougakiuchi; Tadataka Edamura
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Paper Abstract

Since the first demonstration of quantum-cascade lasers (QCLs) in 1994, remarkable progress has been made from the mid-infrared (mid-IR) to terahertz (THz) spectral range. The 1–6 THz spectral range is very attractive for many applications, such as imaging, chem-/bio-sensing, heterodyne detection, and spectroscopy. However, this spectral range still lacks high-performance compact continuous-wave (CW) light sources operable at room temperature. Recently, THz sources based on intracavity difference-frequency generation (DFG) in dual-wavelength mid-IR QCLs have been demonstrated. These devices, known as THz DFG-QCLs, have their active region engineered to exhibit giant intersubband nonlinear susceptibility χ(2) for THz DFG. Recently, we developed THz DFG-QCLs containing an homogeneous active region with dual-upper states (DAU), which exhibit a THz output power of 301 μW with a high mid-IR-to-THz conversion efficiency of 1.2 mW/W2. The DAU active region approach provides a broadband gain bandwidth, and as a result, two wavelength emissions can be obtained without a heterogeneous cascade that has been used previously; this leads to a low threshold current density compared with that obtained from the use of a heterogeneous active region. Here, we present a low threshold THz DFG-QCL based on a λ~6.8 μm DAU active region. The λ~6.8 μm DAU-QCLs have exhibited very low threshold current density as well as broad gain bandwidth. By applying the λ~6.8 μm DAU design approach, the device demonstrates room temperature CW operation without an epidown mounting scheme, where a threshold current density for THz emission has been shown to be low, at 1.3 kA/cm2. Besides, ultra-broadband emission covering 1.6–3.5 THz has been obtained in CW mode below 200 K.

Paper Details

Date Published: 26 January 2018
PDF: 9 pages
Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 105401J (26 January 2018);
Show Author Affiliations
Kazuue Fujita, Hamamatsu Photonics K.K. (Japan)
Akio Ito, Hamamatsu Photonics K.K. (Japan)
Masahiro Hitaka, Hamamatsu Photonics K.K. (Japan)
Tatsuo Dougakiuchi, Hamamatsu Photonics K.K. (Japan)
Tadataka Edamura, Hamamatsu Photonics K.K. (Japan)

Published in SPIE Proceedings Vol. 10540:
Quantum Sensing and Nano Electronics and Photonics XV
Manijeh Razeghi; Gail J. Brown; Jay S. Lewis; Giuseppe Leo, Editor(s)

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