Quanyong Lu
http://www.jos.ac.cn/article/doi/10.1088/1674-4926/40/2/020203
For any laser, high power, good beam quality, and broad electrical frequency tuning range are deemed as the key assets to possess for various applications. Terahertz (THz) quantum cascade laser is no exception. Since its invention in 2001, extensive effort has been devoted to optimizing the laser performance, yet with little success in improving these major aspects on a laser chip simultaneously. Recently, A group led by Qing Hu in MIT has made a major leap with a phase locking approach and achieved these three key performance goals at once. Inspired by the chemistry of hybridization, they can phase lock multiple THz wire lasers by π coupling design. By properly adjusting spacing of adjacent laser element, the laser array can be designed to operate in a coherent symmetric supermode — all collectively radiating in a phase-locked scheme. The demonstrated device exhibits a good level of output power up to 90 mW at continuous-wave operation, and a tight beam pattern of 10° divergence, and a continuous electrical tuning of ~10 GHz at ~3.8 THz. Achieving all three performance metrics means less noise and higher resolution, for more reliable and cost-effective gas sensing, chemical detection, and medical imaging.
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