Terahertz quantum-cascade lasers with lateral distributed-feedback resonators
Fig. 1 (a) Geometry and initial finite-element grid of the lDFB unit cell as used for simulations (periodic in the z-direction). 1: top metallization, 2: highly doped bottom contact layer, 3: bottom metallization, 4: active region, 5: semiinsulating GaAs substrate. (b) Emission spectra for a 0.1×1.2 mm2 lDFB laser (grating period: 8.46 µm). The solid vertical line indicates the OI frequency, while the dashed lines indicate the specified side-band frequencies for the local oscillator.
We developed distributed-feedback (DFB) resonators based on single-plasmon waveguides and first-order lateral DFB (lDFB) gratings [Fig. 1(a)]. These lasers exhibit single-mode emission with output powers of a few mW at operating temperatures, which are accessible by compact Stirling coolers. Based on a rigorous solution of Maxwell’s equations for the DFB unit cell, we developed a general method to calculate the coupling coefficients of lDFB gratings. This allows for an efficient simulation of the resonator properties within the framework of the one-dimensional coupled-mode equations.
One goal for THz astronomy is the heterodyne spectroscopy of the neutral oxygen (OI) fine-structure transition at 4.745 THz, which requires a local oscillator just a few GHz beside this transition frequency. Based on an optimized heterostructure and an adjusted lDFB grating, we achieved single-mode, cw operation around the target frequency [Fig. 1(b)].
Publication
| 1 | Author | M. Wienold , A. Tahraoui , L. Schrottke , R. Sharma , X. Lü , K. Biermann , R. Hey , H.T. Grahn |
| Title |
Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers |
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| Source | Opt. Express , 20 , 11207 ( 2012 ) | |
| Download: PDF | Cite : Bibtex RIS | ||
Paul-Drude-Institut für Festkörperelektronik Leibniz-Institut im Forschungsverbund Berlin e.V.
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