We gratefully acknowledge support by the ERC Advanced Grant "NOLIMITS", the EU FP7 project "NAVOLCHI" and the Marie Curie Career-Integration-Grant "NAPOLI". 

Today’s information society relies on huge computer systems to handle a massive amount of data that grows every day. Computers the size of warehouses are used, where the interconnection of individual processing cores is limiting the total system performance. The interconnects already take up about 50% of the systems power consumption and this value will drastically increase with system complexity and data capacity. This “interconnect bottleneck” can only be overcome by employing optical interconnects for rack-to-rack communication. To sustain the growth of computer performance, we need to develop optical technologies that can be applied at ever shorter distances down to connecting processing cores on the same chip. This implies lasers and photonic components, which are more energy efficient, cheaper and, above all, much smaller.

The support from the European projects Navolchi, NoLimits and Napoli allows us to contribute to a better fundamental understanding of light-matter interaction in nanoscale cavities and develop novel technologies for integration of nanoscale devices in a versatile photonic platform.

Special care needs to be taken when designing laser cavities at the wavelength scale. We study a number of promising novel cavity concepts to find out which are most suitable for small and efficient lasers. Sub-wavelength confinement of light at metal interfaces becomes possible with plasmonic structures [1]. Figure a) shows a scanning electron microscopy (SEM) image of the cross-section of a plasmonic laser fabricated in our clean room. Here, the light is concentrated below 20 nm. In metallo-dielectric structures, which are on the scale of a wavelength, we use the high reflectivity of metal rather than the plasmonic properties, enhancing efficiency [2,3]. Based on this concept, we are currently working on the realization of the pillar lasers with an active region is smaller than 0.2 µm². Figure c) shows an SEM image of a nano-pillar laser structure which is currently being fabricated. Figure d) shows the same pillar coated with Silicon Oxide and a Silver film to form a metallo-dielectric cavity. Finally, we consider the use of photonic crystals for micrometer scale lasers [4]. The precise arrangement of periodic holes in a semiconductor beam allows the control of guiding and reflection properties at the wavelength scale. After first promising simulation results we are now optimizing methods to fabricate such structures in our clean room (Figure b).

Selected Publications:
[1] M. Hill, “Status and prospects for metallic and plasmonic nano-lasers“, J. Opt. Soc. Am. B, Vol. 27, No. 11, 2010.

[2] Dolores Calzadilla, V.M., Geluk, C.T.T., Vries, T. de, Smalbrugge, E., Veldhoven, P.J. van, Ambrosius, H.P.M.M., Heiss, D., Fiore, A. & Smit, M.K. (2013). Fabrication technology of metal-cavity nanolasers in III-V membranes on silicon. Conference Paper : Proceedings of the 18th Annual Symposium of the IEEE Photonics Benelux Chapter, 25-26 November 2013, Eindhoven, The Netherlands, (pp. 243-246). Eindhoven: Technische Universiteit Eindhoven.

[3] Heiss, D., Dolores Calzadilla, V.M., Fiore, A. & Smit, M.K. (2013). Design of a waveguide-coupled nanolaser for photonic integration. In H. Chang, V. Tolstikhin, T Krauss & M Watts (Eds.), Conference Paper : Integrated Photonics Research, Silicon and Nanophotonics (IPRSN), 14-17 July 2013, Rio Grande, (pp. IM2A.3). Rio Grande: Optical Society of America.

[4] Heiss, D., Higuera Rodriguez, A., Dolores Calzadilla, V.M., Fiore, A. & Smit, M.K. (2014). Design of an efficient photonic crystal beam laser. Conference Paper : Proceedings of the 19th Annual Symposium of the IEEE Photonics Benelux Chapter, 3-4 November 2014, Enschede, The Netherlands, accepted or in press.