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Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer

A Retraction to this article was published on 08 March 2013

Abstract

An efficient, room-temperature-operation continuous-wave terahertz source will greatly benefit compact terahertz system development for high-resolution terahertz spectroscopy and imaging applications. Here, we report highly efficient continuous-wave terahertz emission using nanogap electrodes in a photoconductive antenna-based photomixer. The tip-to-tip nanogap electrode structure provides strong terahertz field enhancement and acts as a nano-antenna to radiate the terahertz wave generated in the active region of the photomixer. In addition, it provides good impedance-matching to the terahertz planar antenna and exhibits a lower RC time constant, allowing more efficient radiation, especially at the higher part of the terahertz spectrum. As a result, the output power of the photomixer with the new nanogap electrode structure in the active region is two orders of magnitude higher than for a photomixer with typical interdigitated electrodes. The terahertz emission bandwidth also increases by a factor of more than two.

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Figure 1: Schematic drawings of the fabricated c.w. terahertz photomixers.
Figure 2: Plan-view SEM images of the c.w. terahertz photomixers.
Figure 3: Terahertz output characteristics of the photomixers.
Figure 4: Electric field amplitude in the near field of a modified meander antenna with different photomixers at 1 THz plane-wave illumination.
Figure 5: FDTD simulation of electric field enhancement as a function of gap width and simulation of field intensity distributions within the active region under 1 THz plane-wave illumination.

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Acknowledgements

H.T. and J.H.T. thank M. Tonouchi for helpful discussions. This work is financially supported by the Agency for Science, Technology and Research (A*STAR), Singapore (grant nos 082 1410038, 092 1540097 and 092 1540098) and by the Leverhulme Trust (UK).

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Contributions

J.H.T. conceived the idea and supervised the project. H.T. and Q.Y.W. contributed to the fabrication and characterization of the c.w. terahertz photomixer. M.S., Z.N.C., S.A.M. and B.W. contributed to the theory and simulation. H.T. and S.J.C. contributed to the wafer growth. C.C.C., S.G.Y. and A.J.D. contributed to the nanofabrications. H.T., J.H.T., B.W., M.S. and S.A.M. contributed to writing the manuscript. All authors discussed the results and contributed to the article.

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Correspondence to J. H. Teng.

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The authors declare no competing financial interests.

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Tanoto, H., Teng, J., Wu, Q. et al. Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer. Nature Photon 6, 121–126 (2012). https://doi.org/10.1038/nphoton.2011.322

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