Photonic wire lasers are a new genre of lasers that have a transverse dimension much smaller than the wavelength. Unidirectional emission is highly desirable as most of the laser power will be in the desired direction. Owing to their small lateral dimension relative to the wavelength, however, the mode mostly propagates outside the solid core. Consequently, conventional approaches to attach a highly reflective element to the rear facet, whether a thin film or a distributed Bragg reflector, are not applicable. Here we propose a simple and effective technique to achieve unidirectionality. Terahertz quantum-cascade lasers with distributed feedback (DFB) were chosen as the platform of the photonic wire lasers. Unidirectionality is achieved with a power ratio of the forward/backward of about eight, and the power of the forward-emitting laser is increased by a factor of 1.8 compared with a reference bidirectional DFB laser. Furthermore, we achieved a wall plug power efficiency of ∼1%.

光子线激光器是一种新型的激光器，其横向尺寸远小于波长。由于大多数激光功率将在所需方向上，因此非常需要单向发射。然而，由于其相对于波长的较小横向尺寸，该模式主要在实心核外部传播。因此，不适用于将高反射元件附接到后端面的常规方法，无论是薄膜还是分布式布拉格反射器。在这里，我们提出了一种简单有效的技术来实现单向性。选择了具有分布式反馈（DFB）的太赫兹量子级联激光器作为光子线激光器的平台。单向性的前进/后退功率比约为8，与参考双向DFB激光器相比，前向发射激光器的功率提高了1.8倍。此外，我们实现了墙上插头的电源效率为〜1％。