Phase-locked laser arrays through global antenna mutual coupling


Phase locking of an array of lasers is a highly effective method in beam shaping because it increases the output power and reduces the lasing threshold. Here, we show a conceptually novel phase-locking mechanism based on ‘antenna mutual coupling’ in which laser elements interact through far-field radiations with definite phase relations. This allows a long-range global coupling among the array elements to achieve a robust phase locking in two-dimensional laser arrays. The scheme is ideal for lasers with a deep subwavelength confined cavity, such as nanolasers, whose divergent beam patterns could be used to achieve a strong coupling among the elements in the array. We demonstrated experimentally such a scheme based on subwavelength short-cavity surface-emitting lasers at terahertz frequencies. More than 37 laser elements that span over 8 λo were phase locked to each other, and delivered up to 6.5 mW (in a pulsed operation) single-mode radiation at 3 THz, with a maximum 450 mW A–1 slope efficiency and a near-diffraction-limited beam divergence.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Mutual admittance and electric-field distribution of the QCL.
Figure 2: Magnetic (H) fields inside the laser cavity and far-field beam patterns from 3D FEM simulations.
Figure 3: The laser arrays.
Figure 4: The four quadrants of the laser array.
Figure 5: Type I and Type II grids.


  1. 1

    Hill, M. T. et al. Lasing in metallic-coated nanocavities. Nature Photon. 1, 589–594 (2007).

  2. 2

    Noginov, M. A. et al. Demonstration of a spaser-based nanolaser. Nature 460, 1110–1112 (2009).

  3. 3

    Oulton, R. F. et al. Plasmon lasers at deep subwavelength scale. Nature 461, 629–632 (2009).

  4. 4

    Zhang, J. P. et al. Photonic-wire laser. Phys. Rev. Lett. 75, 2678–2681 (1995).

  5. 5

    Hill, M. T. & Gather, M. C. Advances in small lasers. Nature Photon. 8, 908–918 (2014).

  6. 6

    Ackley, D. E. Single longitudinal mode operation of high power multiple-stripe injection lasers. Appl. Phys. Lett. 42, 152–154 (1983).

  7. 7

    Katz, J., Maargalit, S. & Yariv, A. Diffraction coupled phase-locked semiconductor laser array. Appl. Phys. Lett. 42, 554–556 (1983).

  8. 8

    Brunner, D. & Fischer, I. Reconfigurable semiconductor laser networks based on diffractive coupling. Opt. Lett. 40, 3854–3857 (2015).

  9. 9

    Chen, K. L. & Wang, S. Single-lobe symmetric coupled laser arrays. Electron. Lett. 21, 347–349 (1985).

  10. 10

    Streifer, W., Welch, D., Cross, P. & Scifres, D. Y-junction semiconductor laser arrays. Part I—theory. IEEE J. Quantum Electron. 23, 744–751 (1987).

  11. 11

    Botez, D. & Peterson, G. Modes of phase-locked diode-laser arrays of closely spaced antiguides. Electron. Lett. 24, 1042–1044 (1988).

  12. 12

    Botez, D. High-power monolithic phase-locked arrays of antiguided semiconductor diode lasers. IEE Proc. J. 139, 14–23 (1992).

  13. 13

    Kao, T.-Y., Hu, Q. & Reno, J. L. Phase-locked arrays of surface-emitting terahertz quantum-cascade lasers. Appl. Phys. Lett. 96, 101106 (2010).

  14. 14

    Orlova, E. E. et al. Antenna model for wire lasers. Phys. Rev. Lett. 96, 173904 (2006).

  15. 15

    Faist, J. et al. Quantum cascade laser. Science 264, 553–556 (1994).

  16. 16

    Kohler, R. et al. Terahertz semiconductor heterostructure laser. Nature 417, 156–159 (2002).

  17. 17

    Kumar, S. et al. Surface-emitting distributed feedback terahertz quantum-cascade lasers in metal–metal waveguides. Opt. Express 15, 113–128 (2007).

  18. 18

    Williams, B. S., Kumar, S., Callebaut, H., Hu, Q. & Reno, J. L. Terahertz quantum-cascade laser at λ ≈ 100 µm using metal waveguide for mode confinement. Appl. Phys. Lett. 83, 2124–2126 (2003).

  19. 19

    Balanis, C. A. Antenna Theory: Analysis and Design (John Wiley & Sons, 2012).

  20. 20

    Derneryd, A. G. A theoretical investigation of the rectangular microstrip antenna element. IEEE Trans. Antennas Propag. 26, 532–535 (1978).

  21. 21

    Amanti, M. I., Fischer, M., Scalari, G., Beck, M. & Faist, J. Low-divergence single-mode terahertz quantum cascade laser. Nature Photon. 3, 586–590 (2009).

  22. 22

    Xu, G. et al. Efficient power extraction in surface-emitting semiconductor lasers using graded photonic heterostructures. Nature Commun. 3, 952 (2012).

  23. 23

    Kao, T.-Y., Cai, X., Lee, A. W., Reno, J. L. & Hu, Q. Antenna coupled photonic wire lasers. Opt. Express 23, 17091–17100 (2015).

  24. 24

    van Beijnum, F. et al. Surface plasmon lasing observed in metal hole arrays. Phys. Rev. Lett. 110, 206802 (2013).

  25. 25

    Zhou, W. et al. Lasing action in strongly coupled plasmonic nanocavity arrays. Nature Nanotech. 8, 506–511 (2013).

  26. 26

    Zhang, C. et al. Plasmonic lasing of nanocavity embedding in metallic nanoantenna array. Nano Lett. 15, 1382–1387 (2015).

  27. 27

    Dorofeenko, A. V. et al. Steady state superradiance of a 2D-spaser array. Opt. Express 21, 14539–14547 (2013).

  28. 28

    Li, S., Witjaksono, G., Macomber, S. & Botez, D. Analysis of surface-emitting second-order distributed feedback lasers with central grating phaseshift. IEEE J. Sel. Top. Quantum Electron. 9, 1153–1165 (2003).

Download references


This work is supported by the National Aeronautics and Space Administration and National Science Foundation, and also performed at the Center for Integrated Nanotechnologies, a US Department of Energy, Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multiprogram laboratory 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.

Author information

T.-Y.K. conceived the strategy, designed and fabricated the antenna mutual coupled laser arrays and performed the measurements and analysis, and J.L.R. provided the material growth. All the work was done under the supervision of Q.H.

Correspondence to Qing Hu.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 918 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Kao, T., Reno, J. & Hu, Q. Phase-locked laser arrays through global antenna mutual coupling. Nature Photon 10, 541–546 (2016).

Download citation

Further reading