Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency |
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| Authors: | Guo Wan-Hong Liu Jun-Qi Lu Quan-Yong Zhang Wei Li Lu Wang Li-Jun Liu Feng-Qi and Wang Zhan-Guo |
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| Affiliation: | Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083,China |
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| Abstract: | A 7.8-$\mu $m surface emitting second-order distributed
feedback quantum cascade laser (DFB QCL) structure with metallized
surface grating is studied. The modal property of this structure is
described by utilizing coupled-mode theory where the coupling
coefficients are derived from exact Floquet--Bloch solutions of
infinite periodic structure. Based on this theory, the influence of
waveguide structure and grating topography as well as device length
on the laser performance is numerically investigated. The optimized
surface emitting second-order DFB QCL structure design exhibits a
high surface outcoupling efficiency of 22{\%} and a low threshold
gain of 10~cm$^{ - 1}$. Using a {$\pi $} phase-shift in the centre
of the grating, a high-quality single-lobe far-field radiation
pattern is obtained. |
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| Keywords: | quantum cascade laser Floquet--Bloch expansion distributed feedback lasers surface emission |
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