Terahertz quantum cascade laser array with spatially-separated beams

• Published in: Optics and laser technology 2021-11, Vol.143, p.107346, Article 107346
• Main Authors: Li, Yuan-Yuan, Zhao, Fang-Yuan, Ma, Yu, Li, Wei-Jiang, Liu, Jun-Qi, Liu, Feng-Qi, Luo, Jun-Wei, Zhang, Jin-Chuan, Zhai, Shen-Qiang, Zhuo, Ning, Wang, Li-Jun, Liu, Shu-Man
• Format: Article
• Language: English
• Subjects: Buried sampled grating; Far fields; Focusing; Laser arrays; Lenses; Quantum cascade lasers; Spatially-separated beams; Terahertz
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2021.107346

•A compact lens-coupled THz QCL array with multiple spatially-separated beams has been realized.•Excellent emission characteristics of low divergence angles from 4.1°×3.5° to 7.2°×5.8° and multi-wavelength spectra are obtained. The angular deviation of ~ 10° between adjacent laser guarantees the spatial separation of beams without overlap.•The output intensity after lens improves dramatically for lasers at different positions with a high focusing efficiency. A lens-coupled terahertz (THz) quantum cascade laser (QCL) array with multiple spatially-separated beams is presented. The beam divergence and focusing efficiency after lens are both investigated by simulations and experiments. By integrating an appropriate hyper-hemispherical silicon lens with a well-designed six-element distributed feedback (DFB) QCL array inside the cryostat window, excellent emission characteristics of small divergence angles from 4.1°×3.5° to 7.2°×5.8° and multi-wavelength spectra are realized at 77 K. The deflection angle between adjacent beams is ~ 10°. The output intensity after lens is 113 to 25 times that of original beams with a focusing efficiency ranging from ~ 58% to ~ 37% for lasers at different positions. This method provides a simple solution to form a multi-beam THz source with high intensity and low far-field divergence.