Terahertz (THz) quantum cascade lasers (QCLs) have undergone rapid development since their demonstration, showing high power, broad-tunability, quantum-limited linewidth, and ultra-broadband gain. Typically, to address applications needs, continuous-wave (CW) operation, low-divergent beam profiles and fine spectral control of the emitted radiation, are required. This, however, is very difficult to achieve in practice. Lithographic patterning has been extensively used to this purpose (via distributed feedback (DFB), photonic crystals or microcavities), to optimize either the beam divergence or the emission frequency, or, both of them simultaneously, in third-order DFBs, via a demanding fabrication procedure that precisely constrains the mode index to 3. Here, we demonstrate wire DFB THz QCLs, in which feedback is provided by a sinusoidal corrugation of the cavity, defining the frequency, while light extraction is ensured by an array of surface holes. This new architecture, extendable to a broad range of far-infrared frequencies, has led to the achievement of low-divergent beams (10°), single-mode emission, high slope efficiencies (250 mW/A), and stable CW operation.

中文翻译：

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连续波高效低发散太赫兹线激光器。

太赫兹（THz）量子级联激光器（QCL）自演示以来经历了快速发展，表现出高功率、宽可调性、量子限制线宽和超宽带增益。通常，为了满足应用需求，需要连续波 (CW) 操作、低发散光束轮廓以及对发射辐射的精细光谱控制。然而，这在实践中很难实现。光刻图案化已广泛用于此目的（通过分布式反馈（DFB）、光子晶体或微腔），以优化光束发散或发射频率，或者在三阶 DFB 中同时优化两者，通过要求严格的将模式指数精确限制为 3 的制造过程。在这里，我们演示了线 DFB THz QCL，其中反馈由腔体的正弦波纹提供，定义频率，同时通过表面孔阵列确保光提取。这种新架构可扩展到广泛的远红外频率，实现了低发散光束 (10°)、单模发射、高斜率效率 (250 mW/A) 和稳定的 CW 操作。