Collective Mie-resonances for active elements in silicon photonics

• Applicant: Professor Dr. Jörg Schilling
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429807842

The project aims at studying silicon compatible Mie resonators and their ensembles containing embedded Ge-based quantum emitters with luminescence wavelengths in the telecom spectral region. These resonators possess collective resonances which can be tuned and controlled by the size and geometry of the individual nanoresonators. In the project, we suggest to enhance the luminescence efficiency via the Purcell-effect, control the radiation directionality, and increase the light-matter interaction of Ge-based emitter systems. The final goal is to obtain stimulated emission leading us to the development of very compact all-dielectric nanolasers.Three different concepts will be theoretically as well as experimentally investigated: Mie-resonator chains, Bound states in continuum (BIC) and nanoantennas. They are geared to increase the local density of states or Q-factor of the collective resonances in the near IR and to control the radiation directivity.In chains of periodically arranged Mie-resonators the coupling between individual Mie-resonances and appearing Bragg-resonances will be controlled to form photonic band edges and flat bands to enhance the photonic density of states. Strongly enhanced Q-factors of the resulting collective resonances will be achieved by overall cancellation of the far-field radiation due to the out-of-phase superposition of the far-fields from the individual resonators. For the formation of a BIC the structure parameters of the Mie-resonators are chosen in such a way that two different Mie-resonances are superposed at the same resonant frequency leading to the cancellation of their corresponding far fields. Finally, the spatial arrangement of the individual resonators is used to obtain far reaching control of the directionality of the emitted light e.g. by realising a dielectric Yagi-Uda antenna. The studied emitter systems comprise randomly arranged Ge-quantum dots, ordered Ge-quantum dots and n-type, tensile strained Ge. Using MBE-growth the Ge-quantum dots will be embedded inside the Mie resonators and can therefore couple efficiently to the Mie-resonances. Using the site-controlled growth of the Ge-quantum dots we plan to place them at specific positions within the resonators to allow the study of position dependent coupling between the local mode field and the emitters. Eventually highly n-doped, tensile strained Ge is fabricated using an out-of-equilibrium MBE-growth process and a deposited stressed SiNx-layer leading to a high probability of direct transitions in the strained Ge. The prospects to achieve a Mie-resonator nanolaser will be evaluated.Dark-field spectroscopy, steady-state and time-resolved micro-photoluminescence as well as back focal plane imaging of the emission will be used to determine the spectral positions and Q-factors of the Mie-resonances, obtain the experimental Purcell-factor and evaluate the emission directionality.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research, until 3/2022
• Cooperation Partners: Dr. Alexey Novikov, until 3/2022; Dr. Mihail Petrov, until 3/2022