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Phase-locked photonic wire lasers by π coupling


The term photonic wire laser is now widely used for lasers with transverse dimensions much smaller than the wavelength. As a result, a large fraction of the mode propagates outside the solid core. Here, we propose and demonstrate a scheme to form a coupled cavity by taking advantage of this unique feature of photonic wire lasers. In this scheme, we used quantum cascade lasers with antenna-coupled third-order distributed feedback grating as the platform. Inspired by the chemistry of hybridization, our scheme phase-locks multiple such lasers by π coupling. With the coupled-cavity laser, we demonstrated several performance metrics that are important for various applications in sensing and imaging: a continuous electrical tuning of ~10 GHz at ~3.8 THz (fractional tuning of ~0.26%), a good level of output power (~50–90 mW of continuous-wave power) and tight beam patterns (~100 of beam divergence).

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Fig. 1: Full-wave simulations of DFB with and without antenna loop.
Fig. 2: Experimental verification of π-coupled ADFB.
Fig. 3: Experimental set-up for measuring frequency difference with kHz resolution.
Fig. 4: Frequency tuning of π-coupled ADFBs.
Fig. 5: Result of a π-coupled ADFB optimized for output power.
Fig. 6: Versatility of the π-coupled scheme for higher numbers of ADFBs.

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Data availability

The data that support the plots within this paper and other finding of this study are available from the corresponding author upon reasonable request.


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This work is supported by the National Aeronautics and Space Administration (NASA) at MIT. 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 (DOE) Office of Science. Sandia National Laboratories is a multi-program 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 M. Belanger of MIT Edgerton shop for guidance in preparing the copper heat sinks. A.K. also acknowledges useful discussions with A. K. Paulsen, Y. Yang and T. Zeng.

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A.K. conceived the idea, strategy, designed and fabricated the devices, performed the measurements and analysis, and wrote the manuscript. J.L.R. performed the molecular-beam epitaxy growth. All the work was done under the supervision of Q.H.

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Correspondence to Qing Hu.

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Khalatpour, A., Reno, J.L. & Hu, Q. Phase-locked photonic wire lasers by π coupling. Nature Photon 13, 47–53 (2019).

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