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Thresholdless nanoscale coaxial lasers


The effects of cavity quantum electrodynamics (QED), caused by the interaction of matter and the electromagnetic field in subwavelength resonant structures, have been the subject of intense research in recent years1. The generation of coherent radiation by subwavelength resonant structures has attracted considerable interest, not only as a means of exploring the QED effects that emerge at small volume, but also for its potential in applications ranging from on-chip optical communication to ultrahigh-resolution and high-throughput imaging, sensing and spectroscopy. One such strand of research is aimed at developing the ‘ultimate’ nanolaser: a scalable, low-threshold, efficient source of radiation that operates at room temperature and occupies a small volume on a chip2. Different resonators have been proposed for the realization of such a nanolaser—microdisk3 and photonic bandgap4 resonators, and, more recently, metallic5,6, metallo-dielectric7,8,9,10 and plasmonic11,12 resonators. But progress towards realizing the ultimate nanolaser has been hindered by the lack of a systematic approach to scaling down the size of the laser cavity without significantly increasing the threshold power required for lasing. Here we describe a family of coaxial nanostructured cavities that potentially solve the resonator scalability challenge by means of their geometry and metal composition. Using these coaxial nanocavities, we demonstrate the smallest room-temperature, continuous-wave telecommunications-frequency laser to date. In addition, by further modifying the design of these coaxial nanocavities, we achieve thresholdless lasing with a broadband gain medium. In addition to enabling laser applications, these nanoscale resonators should provide a powerful platform for the development of other QED devices and metamaterials in which atom–field interactions generate new functionalities13,14.

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Figure 1: Nanoscale coaxial laser cavity.
Figure 2: Simulation of the electromagnetic properties of nanoscale coaxial cavities.
Figure 3: Optical characterization of nanoscale coaxial cavities of structure A at 4.5 K and room temperature, showing lasing.
Figure 4: Optical characterization of nanoscale coaxial cavities of structure B at 4.5 K, showing thresholdless lasing.


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We acknowledge support from the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF), the NSF Center for Integrated Access Networks (CIAN), the Cymer Corporation and the US Army Research Office. M. Khajavikhan thanks the personnel of the UCSD Nano3 facilities for their help and support, T. Javidi and J. Leger for technical discussions regarding the analysis of the data and profile of the beam, and graduate student J. Shane for her help with editing the document.

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Authors and Affiliations



M. Khajavikhan conceived the idea of thresholdless laser using nanoscale coaxial structures. The electromagnetic design, simulation, and analysis of the structures were carried out by M. Khajavikhan, A.M. and V.L. Fabrication of the devices was carried out by M. Khajavikhan and J.H.L. The optical measurements were performed by A.S. and M. Khajavikhan. The rate equation model was developed by M. Katz. The optical characterization and analysis of laser behaviour was carried out by M. Khajavikhan, M. Katz, A.M., B.S. and Y.F. The manuscript was written by M. Khajavikhan, with contributions from A.M., M. Katz, Y.F., A.S., B.S. and V.L.

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Correspondence to M. Khajavikhan.

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The authors declare no competing financial interests.

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Khajavikhan, M., Simic, A., Katz, M. et al. Thresholdless nanoscale coaxial lasers. Nature 482, 204–207 (2012).

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