1 Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Beijing 100083, China; 2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China; 3 Beijing Academy of Quantum Information Sciences, Beijing 100193, China
Abstract A beam steering effect of high-power quantum cascade (QC) lasers emitting at ∼ 4.6 μ m was investigated. The continuous wave (CW) output power of an uncoated, 6-mm-long, 7.5-μ m-wide buried-heterostructure QC laser at 25 °C was as high as 854.2 mW. The maximum beam steering angle was offset by 14.2° from the facet normal (0°) in pulsed mode. The phenomenon was judged explicitly by combining the diffraction limit theory and Fourier transform of the spectra. It was also verified by finite element method software simulation and the calculation of two-dimensional (2D) effective-index model. The observed steering is consistent with a theory for coherence between the two lowest order lateral modes. Therefore, we have established an intrinsic linkage between the spectral instabilities and the beam steering by using the Fourier transform of the spectra, and further presented an extremely valid method to judge the beam steering. The content of this method includes both three equidistant peak positions in the Fourier transform of the spectra and the beam quality located between once the diffraction limit (DL) and twice the DL.
Fund: Project supported by the National Basic Research Program of China (Grant Nos. 2018YFA0209103 and 2018YFB2200504), the National Natural Science Foundation of China (Grant Nos. 61991430, 61774146, 61790583, 61674144, and 61774150), and the Key Projects of the Chinese Academy of Sciences (Grant Nos. 2018147, YJKYYQ20190002, QYZDJ-SSW-JSC027, and XDB43000000).
Very low threshold operation of quantum cascade lasers Yan Fang-Liang (闫方亮), Zhang Jin-Chuan (张锦川), Yao Dan-Yang (姚丹阳), Liu Feng-Qi (刘峰奇), Wang Li-Jun (王利军), Liu Jun-Qi (刘峻岐), Wang Zhan-Guo (王占国). Chin. Phys. B, 2015, 24(2): 024212.
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