High-resolution terahertz semiconductor spectroscopy using quantum-cascade lasers: Develop-ment of appropriate laser sources for 2.7-3.3 and 5.0-5.7 THz
Final Report Abstract
In summary, we successfully improved our model by implementing realistic scattering rates for the interaction of electrons with longitudinal optical phonons into our fast simulation tool so that the most severe drawback of the previous empirical model, namely the underestimation of nonradiative transitions between states of similar parity, can be mastered. The introduction of the GaAs/AlAs materials system for THz QCLs allowed for the development of lasers with an increased wall plug efficiency and correspondingly reduced threshold current density compared to similar GaAs/(Al,Ga)As QCLs. We investigated the chemical composition profile of THz QCLs by means of transmission electron microscopy and showed that these profiles can be well reproduced by our model. Based on the new model and on GaAs/AlAs heterostructures, we developed lasers emitting at frequencies above 5.6 THz. We developed a method for the fine tuning of the emission frequencies to particular target frequencies with an accuracy of about 1 GHz by polishing the front facet of mounted lasers. We succeeded in preparing two-section QCLs for single-mode emission employing a focused ion beam. Finally, external dynamic tuning was demonstrated by rear-facet illumination with near-infrared diode lasers for multi-mode and single-mode QCLs.
Publications
- Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination, Appl. Phys. Lett. 108, 191106, 5 pages (2016)
M. Hempel, B. Röben, L. Schrottke, H.-W. Hübers, and H. T. Grahn
(See online at https://doi.org/10.1063/1.4949528) - Real-time terahertz imaging through self-mixing in a quantum-cascade laser, Appl. Phys. Lett. 109, 011102, 5 pages (2016)
M. Wienold, T. Hagelschuer, N. Rothbart, L. Schrottke, K. Biermann, H. T. Grahn, and H.-W. Hübers
(See online at https://doi.org/10.1063/1.4955405) - Continuous tuning of two-section, single-mode terahertz quantum-cascade lasers by fiber-coupled, near-infrared illumination, AIP Adv. 7, 055201, 6 pages (2017)
M. Hempel, B. Röben, M. Niehle, L. Schrottke, A. Trampert, and H. T. Grahn
(See online at https://doi.org/10.1063/1.4983030) - Real-time gas sensing based on optical feedback in a terahertz quantum-cascade laser, Opt. Express 25, 30203–30213 (2017)
T. Hagelschuer, M. Wienold, H. Richter, L. Schrottke, H. T. Grahn, and H.-W. Hübers
(See online at https://doi.org/10.1364/OE.25.030203) - Terahertz quantumcascade lasers as high-power and wideband, gapless sources for spectroscopy, Opt. Express 25, 16282–16290 (2017)
B. Röben, X. Lü, M. Hempel, K. Biermann, L. Schrottke, and H. T. Grahn
(See online at https://doi.org/10.1364/OE.25.016282) - Doppler-free spectroscopy with a terahertz quantum-cascade laser, Opt. Express 26, 6692–6699 (2018)
M. Wienold, T. Alam, L. Schrottke, H. T. Grahn, and H.-W. Hübers
(See online at https://doi.org/10.1364/OE.26.006692)
