%A Yong-Qiang Sun(孙永强), Jin-Chuan Zhang(张锦川), Feng-Min Cheng(程凤敏), Chao Ning(宁超), Ning Zhuo(卓宁), Shen-Qiang Zhai(翟慎强), Feng-Qi Liu(刘峰奇), Jun-Qi Liu(刘俊岐), Shu-Man Liu(刘舒曼), and Zhan-Guo Wang(王占国) %T Beam steering characteristics in high-power quantum-cascade lasers emitting at 4.6 μ m %0 Journal Article %D 2021 %J Chin. Phys. B %R 10.1088/1674-1056/abd6fe %P 34211- %V 30 %N 3 %U {https://cpb.iphy.ac.cn/CN/abstract/article_123296.shtml} %8 2021-02-22 %X 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.