During the last two decades, integrated photonics based on silicon photonics have gained a lot of interest in research and industry developments. The rapid increase of data traffic makes drastic changes to more efficient technologies like full optical data transmission necessary. Recent developments in optical communication mainly rely on hybrid integration of III-V lasers on top of the silicon platform. This procedure is not only costly in terms of III-V wafers, but especially the assembly can reach up to 80% of the fabrication cost.

These happy partners (AMIRESAMO GmbHCIC biomaGUNECSICFAU Erlangen-NürnbergUniversity of CambridgeUniversity of Hull, UniSiegen) met in person at the beautiful University of Cambridge to reflect on the key achievements of an idea to integrate light sources directly into the photonic circuits by exploiting the self-assembly of active colloids on chips. Large scale integration of efficient (laser) light sources would open the field to many new applications such as point of care medicine, environmental sensing as well as quantum photonics.

The project passed the half way of the duration and here are some of our main achievements:

Work Package 1: Within WP1 Theoretical design of colloidal light sources, the roadmap of nanoantennas for the light source was identified and selected. The activities focused on nanorod gap antennas, as an optimal structure to accomplish the objectives of the POSEIDON project. Our study of interfacial assembly of dimer rod nanoantennas is 100% complete, of bulk assembly of dimer rod nanoantennas is 80% complete, on the optimisation of plasmonic structures for light sources and Zero index materials is 100% fulfilled. The study of multishell nanoparticles to obtain zero-index-materials (ZIMs), and the effectiveness of the ZIMs as a perfect coupler between an emitter-nanoantena system and a waveguide was assessed. The conclusion so far is that the required particles are too large for this task and our focus is shifted to the other configurations.

Work Package 2: Synthesis of colloidal building blocks: Development of particle synthesis protocols for polystyrene and PDVB laytex particles by miniemulsion and classical emulsion polymerization was completed. Synthesis of new RAFT polymers from different monomer systems for modification of quantum dots (QDs) and gold (Au) nanoparticles (NPs) were completed. Modification of QDs with RAFT polymer for particle transfer from organic apolar to aqueous medium was successful. Synthesis of metal nanoparticles for nanoantenna light sources was completed with final evaluation that refers to the synthesis of nanoparticle building blocks for the fabrication of nanoantenna light sources (in agreement with simulation results from WP1).

Work Package 3: Integrated assembly of colloidal light sources has focused on the theoretical design of such materials and identified core-shell particle assemblies as a promising avenue. There has been excellent progress in the self-assembly of nanoantenna structures. The consortium has agreed on four distinct strategies as outlined in WP1. All strategies are subjected to rigorous examination, both in terms of synthetic feasibility and theoretical assessment of emission enhancement. To this point, dimer nanoantennas and patch nanoantennas have emerged as feasible candidates.  As a side aspect with potential relevance to tailor emission properties, we successfully prepared chiral nanoantenna arrays that exhibit chiroptical properties. We are 100% capable of producing crescent shape and disk shape gold nano-antennas.

Work Package 4: Creation of electrically pumped light source: The main structures were developed and their characterization is ongoing.  More nanoantenna structures need to be evaluated to extract efficiency and directionality of the light emission. Integrating monolayer QDs and nanoparticles on an optimized photonic chip fabricated by AMO to create electrically pumped nano-antennas was completed. Activities in this WP were also focused on exploring new nano-antennas, blocking layers etc. for reducing electrical junction breakdown and enhancing emission efficiencies of the electrically pumped nanoantennas.

Work Package 5: Creation and optimization of PIC: The fabrication runs so far have been successful with satisfactory preliminary results. Gaps for improvements have been identified and are being addressed. New proposed process flows are a good direction to reach the project goals and will soon be fully evaluated. All the necessary basic calculations of particle-on-mirror configuration have been completed by AMO. The process margin was verified. Additionally, we have identified few more configurations, which might increase the coupling efficiency. The necessary data will be discussed with CSIC to perform further simulations. Currently we are one step away (QD+Au NPs) to form the first generation of the integrated optically pumped light source.

Work Package 6: Dissemination & Exploitation: Mid-term report on dissemination and second version of the exploitation plan were prepared. Several communication materials have been created: logo & templates, factsheet, press release, LinkedIn page with growing number of followers (156 followers), business cards (with QR code link to website), website that was visited by 4000 users during Jan 2021-June 2022.

Work Package 7: Project Management & coordination: Three high-level project meetings have been held (M18, M24, M30 meeting) and an EC review meeting in month 15. Additional monthly WP web conferences were organized and topic specific meetings took place in smaller groups.