Abstract-Sub-terahertz and terahertz generation in long-wavelength quantum cascade lasers

Kazuue Fujita, Shohei Hayashi, Akio Ito, Masahiro Hitaka, Tatsuo Dougakiuchi

https://www.degruyter.com/view/j/nanoph.ahead-of-print/nanoph-2019-0238/nanoph-2019-0238.xml

Terahertz quantum cascade laser sources with intra-cavity non-linear frequency mixing are the first room-temperature electrically pumped monolithic semiconductor sources that operate in the 1.2–5.9 THz spectral range. However, high performance in low-frequency range is difficult because converted terahertz waves suffer from significantly high absorption in waveguides. Here, we report a sub-terahertz electrically pumped monolithic semiconductor laser. This sub-terahertz source is based on a high-performance, long-wavelength (λ ≈ 13.7 μm) quantum cascade laser in which high-efficiency terahertz generation occurs. The device produces peak output power of 11 μW within the 615–788 GHz frequency range at room temperature. Additionally, a source emitting at 1.5 THz provides peak output power of 287 μW at 110 K. The generated terahertz radiation of <2 THz is mostly attributable to the optical rectification process in long-wavelength infrared quantum cascade lasers.

Abstract-Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation

Luigi Consolino.  Seungyong Jung,  Annamaria Campa, Michele De Regis, Shovon Pal, Jae Hyun Kim, Kazuue Fujita, Akio Ito, Masahiro Hitaka, Saverio Bartalini, Paolo De Natale, Mikhail A. Belkin, Miriam Serena Vitiello,

http://advances.sciencemag.org/content/3/9/e1603317


Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10−10. The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.

Abstract-Ultra-broadband room-temperature terahertz quantum cascade laser sources based on difference frequency generation

Kazuue Fujita, Masahiro Hitaka, Akio Ito, Masamichi Yamanishi, Tatsuo Dougakiuchi, and Tadataka Edamura
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-15-16357

We present ultra-broadband room temperature monolithic terahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation, emitting continuously more than one octave in frequency between 1.6 and 3.8 THz, with a peak output power of ~200 μW. Broadband terahertz emission is realized by nonlinear mixing between single-mode and multi-mode spectra due to distributed feedback grating and Fabry-Perot cavity, respectively, in a mid-infrared QCL with dual-upper-state active region design. Besides, at low temperature of 150 K, the device produces a peak power of ~1.0 mW with a broadband THz emission centered at 2.5 THz, ranging from 1.5 to 3.7 THz.

© 2016 Optical Society of America

Full Article  |  PDF Article