HIgh-index dielectric nanostructures for controlled LIGHT emission and propagation (HiLight) – HiLight

A current challenge in the information and communication society is to provide new high-speed, low-consumption photonic devices integrated on chip. In that context, silicon photonics has proved to be very efficient as the optical components (waveguides, couplers, modulators…) can be implemented with the electronic Si-based components using the same CMOS technology. However, the production and integration of efficient light sources and photodetectors at the nanoscale is still lacking.
The HiLight project aims at realizing efficient light sources based on quantum emitters coupled to high-index dielectric nanostructures, working at room temperature, scalable to operate at any wavelength in the visible to near infrared range. Hence, the consortium has identified three scientific and technological challenges that have to be addressed, which are: enhanced emission rate of the emitters (Purcell effect), directivity of the emission in a chosen direction, and waveguide coupling for propagation or remote excitation of emitters, ideally on a broadband spectrum.
The HiLight project methodology to tackle these challenges is:
- Study of high-index dielectric nanoantennas coupled to different quantum emitters. Silicon of germanium nanostructures will be designed for directivity control, thanks to Fano-like interference between broad dipole resonances and sharp higher order modes. They will be then fabricated by electron beam lithography and reactive ion etching from engineered substrates. Silicon is an excellent candidate with high refractive index in the visible spectrum and a weak optical absorption, allowing producing low-loss devices.
- Selective control of the emission decay rate of magnetic and electric dipoles. The Local Density of Optical Sates (LDOS) is a key parameter for enhanced Purcell effect, and LDOS engineering is included in the nanostructure design. In dielectric nanostructures, the magnetic field can be strongly enhanced, much more than the electric field, so that emitters such as rare-earth ions supporting magnetic dipole transitions of similar strength than the electric dipole transitions will be used as emitters to obtain a higher magnetic Purcell effect than the electric Purcell effect.
- Influence of both position and orientation of the emitting dipoles relative to the nanoantenna. Numerical simulations show that optimized emission rate and directivity are obtained for both specific spatial orientation and position of the emitting dipole. Experimentally, specific emitters such as transition metal dichalcogenide (TMD) monolayers that have well defined, spectrally separated in- and out-of plane excitons and that can be dimensioned to the nanoantenna, will be used to overcome this issue.
- Coupling to a waveguide wavelength-dependent transmission or remote excitation of the emitters through the waveguide.
HiLight is based on a consortium of six laboratories that covers the production of engineered substrates such as Silicon or Germanium on Silica (SOS or GeOS), the fabrication of nanostructures in these substrates and the deposition of quantum emitters, and the optical property studies to the realization of a proof-of-concept device making progress on all the above mentioned challenges. The nanoantenna design and the coupling of the emitters (rare-earth doped clusters, NV colored centers in nanodiamonds, TMD monolayer) to the nanoantennas will be obtained first by numerical simulations, which will be also used to model experimental results and provide Figure-of-Merits of an optimized optical nanosource.