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End date: 2019 × Start date: 2010 × DDC: 620 × Version: publishedVersion × Subject: Infrared and far-infrared lasers × Subject: Semiconductor lasers ×

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Now showing 1 - 2 of 2
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    Terahertz quantum-cascade lasers as high-power and wideband, gapless sources for spectroscopy
    (Washington, DC : Optical Society of America, 2017) Röben, Benjamin; Lü, Xiang; Hempel, Martin; Biermann, Klaus; Schrottke, Lutz; Grahn, Holger T.
    Terahertz (THz) quantum-cascade lasers (QCLs) are powerful radiation sources for high-resolution and high-sensitivity spectroscopy with a discrete spectrum between 2 and 5 THz as well as a continuous coverage of several GHz. However, for many applications, a radiation source with a continuous coverage of a substantially larger frequency range is required. We employed a multi-mode THz QCL operated with a fast ramped injection current, which leads to a collective tuning of equally-spaced Fabry-Pérot laser modes exceeding their separation. A continuous coverage over 72 GHz at about 4.7 THz was achieved. We demonstrate that the QCL is superior to conventional sources used in Fourier transform infrared spectroscopy in terms of the signal-to-noise ratio as well as the dynamic range by one to two orders of magnitude. Our results pave the way for versatile THz spectroscopic systems with unprecedented resolution and sensitivity across a wide frequency range.
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    Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers
    (Washington, DC : Optical Society of America, 2012) Wienold, M.; Tahraoui, A.; Schrottke, L.; Sharma, R.; Lü, X.; Biermann, K.; Hey, R.; Grahn, H.T.
    We report on terahertz quantum-cascade lasers (THz QCLs) based on first-order lateral distributed-feedback (lDFB) gratings, which exhibit continuous-wave operation, high output powers (>8 mW), and single-mode emission at 3.3–3.4 THz. A general method is presented to determine the coupling coefficients of lateral gratings in terms of the coupled-mode theory, which demonstrates that large coupling strengths are obtained in the presence of corrugated metal layers. The experimental spectra are in agreement with simulations of the lDFB cavities, which take into account the reflective end facets.