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Unidirectional photonic wire laser


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%.

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Figure 1
Figure 2: Simple model for unidirectional third-order DFB.
Figure 3: Fabrication and measurement strategy.
Figure 4: Measurement results for a unidirectional third-order DFB.
Figure 5: Measurement results for a unidirectional third-order DFB.

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This work is supported by the National Aeronautics and Space Administration and the National Science Foundation at the Massachusetts Institute of Technology. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy Office of Science. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. A.K. acknowledges support from Natural Science and Engineering Research Council of Canada.

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A.K. conceived the idea and strategy, designed and fabricated the devices and performed the measurements and analysis, and J.L.R. provided the material growth. A.K. benefited from in-depth discussions regarding the simulation and design strategy with N.P.K. All the work was done under the supervision of Q.H.

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Correspondence to Qing Hu.

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The authors declare no competing financial interests.

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Khalatpour, A., Reno, J., Kherani, N. et al. Unidirectional photonic wire laser. Nature Photon 11, 555–559 (2017).

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