4 February 2013 Phase-locking of surface-emitting THz quantum cascade laser arrays
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We first discuss and review a novel technique to obtain efficient surface-emission in terahertz quantum cascade lasers (THz-QCLs). We report high-power, single-mode surface-emission by using graded photonic heterostructures (GPH) as resonators. Peak output powers of ~100 mW and differential efficiency of 230mW/A are achieved at frequency ~ 3.4THz, the maximum operation temperature being 120K in pulsed mode. Combining with the active region based on the bound-to-continuum design, we also achieved continuous-wave (CW) operation of GPH THz QC lasers, with the maximum output power of 3.8 mW at 2.7THz. We then discuss the prospects to develop phase-locked arrays of these devices, in order to take advantage of their good wall-plug efficiency (<0.3%) and single-lobed directional beam pattern. As an initial result, a very robust approach to phase-lock second-order distributed feedback (DFB) THz QC laser arrays (pairs in this case) is demonstrated.
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Gangyi Xu, Gangyi Xu, Yacine Halioua, Yacine Halioua, Raffaele Colombelli, Raffaele Colombelli, Suraj P. Khanna, Suraj P. Khanna, Lianhe Li, Lianhe Li, Edmund H. Linfield, Edmund H. Linfield, A. Giles Davies, A. Giles Davies, Harvey Beere, Harvey Beere, David A. Ritchie, David A. Ritchie, "Phase-locking of surface-emitting THz quantum cascade laser arrays", Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86310F (4 February 2013); doi: 10.1117/12.2004125; https://doi.org/10.1117/12.2004125

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