Integrated Nanocavity Plasmon Light Sources for On-Chip Optical Interconnects Ke Liu, †,‡ Ning Li,* ,§ Devendra K. Sadana, § and Volker J. Sorger* ,† † Department of Electrical and Computer Engineering, School of Engineering and Applied Science, George Washington University, Washington, DC 20052, United States ‡ The Key Laboratory of Optoelectronics Technology, Ministry of Education, College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, People’s Republic of China § IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598, United States * S Supporting Information ABSTRACT: Next generation on-chip light sources require high modulation bandwidth, compact footprint, and efficient power consumption. Plasmon-based sources are able to address the footprint challenge set by both the diffraction limited of light and internal laser physics such as plasmon utilization. However, the high losses, large plasmonic-momentum of these sources hinder efficient light coupling to on-chip waveguides, thus, questioning their usefulness. Here we show that plasmon light sources can be useful devices; they can deliver efficient outcoupling power to on-chip waveguides and are able to surpass modulation speeds set by gain-compression. We find that waveguide-integrated plasmon nanocavity sources allow to transfer about ∼60% of their emission into planar on-chip waveguides, while sustaining a physical small footprint of ∼0.06 μm 2 . These sources are able to provide output powers of tens of microwatts for microamp-low injection currents and reach milliwatts for higher pump rates. Moreover, the direct modulation bandwidth exceeds that of classical, gain compression-limited on-chip sources by more than 200%. Furthermore, these novel sources feature high power efficiencies (∼1 fJ/bit) enabled by both minuscule electrical capacitance and efficient internal photon utilization. Such strong light-matter interaction devices might allow redesigning photonic circuits that only demand microwatts of signal power in the future. KEYWORDS: laser, nanocavity, plasmon, photonics integration, rate equations I n the past decade, photonic technologies have become universal in data communications. The dense integration of photonic communication links has potential to deliver both high data throughput and bit-densities, while minimizing power consumption and energy dissipation. 1,2 In particular, solutions are needed to address both the increasing power density and data rate bottleneck between computation and communica- tion. 3 However, the required on-chip light sources for the photonic links are challenged by (1) large footprints due to the diffraction limit of light, (2) low threshold efficiencies owing to small spontaneous emission coupling factors, β, leading to high power consumption (i.e., energy-per-bit), (3) temperature sensibilities when high-quality cavities are deployed, and (4) slow modulation speeds because of gain compression effects and parasitic electrical capacitances. As a result, network-on- chip light sources are therefore often considered off-chip. 4 The emerging field of plasmonics, coherent electromagneti- cally driven electronic oscillations at metal-dielectric interfaces, 5 has demonstrated on-chip laser devices that address some of the above challenges; these include compact light sources below the diffraction limit, 6-8 operating at cryo 9,10 and room temperature, 11,12 and pulsed 13 and continuous wave oper- ation. 14 However, these laboratory demonstrations are often unsuitable for chip integration due to a variety of limitations such as incompatibilities to telecom frequencies of the gain medium, photonic platform integration, and inability to deliver Received: August 24, 2015 Published: January 19, 2016 Article pubs.acs.org/journal/apchd5 © 2016 American Chemical Society 233 DOI: 10.1021/acsphotonics.5b00476 ACS Photonics 2016, 3, 233-242