CIRCULATING LIGHT ON ANY PHOTONIC PLATFORM

Project Information

CIRCULIGHT

Grant agreement ID: 101129645

DOI

10.3030/101129645

EC signature date 21 February 2024

Start date 1 April 2024

End date 30 September 2027

Funded under

• The European Innovation Council (EIC)

Total cost

€ 2 908 754,98

EU contribution

€ 2 908 754,98

Coordinated by

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
France

Periodic Reporting for period 1 - CIRCULIGHT (CIRCULATING LIGHT ON ANY PHOTONIC PLATFORM)

Reporting period: 2024-04-01 to 2025-03-31

Summary of the context and overall objectives of the project

The main objective of CIRCULIGHT is to develop a new technology for monolithically integrated optical circulators and isolators which is compatible with any Photonic Integrated Circuits (PICs) platform. Extreme miniaturization and integration of multiple photonic functions into PICs suffer from the lack of this essential building block: the optical circulator is a central device that allows the others to be brought together in PICs without unwanted interactions. Such a non-reciprocal (NR) element would enable full integration of active and passive devices and diversify circuit architectures. The extraordinary potential of photonics and its decisive advantage to provide energy consumption reduction will impact across a wide range of applications of high economic and societal value, such as optical fiber communications, data processing, sensing, neuromorphic computing, medical diagnosis and food industry (labs-on-chip), etc.. With that purpose, the methodology of CIRCULIGHT includes the scientific and technological breakthroughs leading to the new device, as well as the co-creation of its exploitation roadmap, including the identification of key technology and market development activities, infrastructure and facilities, training and education.
In the landscape of previous non-reciprocal devices, CIRCULIGHT explores a new approach, which combines Transverse Magneto-Optical Effect (TMOKE) with a mode-coupling mechanism in a plasmonic slot waveguide: this so-called Magneto-Biplasmonic (MBP) concept enables compact and broadband non-reciprocal devices, even with low gyrotropy MO material such as MO composite sol-gel material which can be deposited on any photonic platform.
In that context, the general objectives of the project are to demonstrate:
Objective 1 MO material universal deposition technique (nanoparticle-composite sol-gel) into guided photonic device
Objective 2 Magneto-biplasmonic (MBP) concept demonstration and relevance for integrated circulator
Objective 3 Proof-of-concept of user-oriented laser-circulator-receiver integration on any photonic platform
Objective 4 Stakeholder co-created application and exploitation roadmap towards societal impact

More precisely, we will consider the case of three-port circulators, based on MBP effect, with gold or silver as plasmonic metal and composite sol-gel as MO material, integrated on InP or silicon platform (Fig. 1).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The two main technical and scientific activities of this period were focused on the design and numerical modelling of the MO circulator, and on the MO material development. Activities related to the device technological fabrication and characterization, and to the analysis for exploitation roadmap and societal impact of this technology have started but first results are expected later in the project.
For all the ongoing activities, strong interactions between the partners have been established to ensure technological compatibilities: materials choice, MO material performance targets and the geometry of the waveguides (modification of the stacked layers) are continuously discussed between the partners in charge of the design and partners in charge of the fabrication.
The numerical electromagnetic analysis of the magneto-optic slot waveguide configuration has provided general design rules to reach the targeted performance, showing the compromises that can be made by adjusting the refractive index of the MO material, the gyrotropic coefficient, the thickness and/or the choice of metal (gold or silver). Different designs were proposed and their compatibility with fabrication discussed.
Designs of the magneto-plasmonic slot waveguide for low-loss 3-ports circulator have also been reported, as illustrated in Fig. 2. The designed slot waveguide has a variable width that allows the energy of the propagating modes to be transferred to one side of the slot within a minimum distance, and to the output port oriented at an angle of 120° to the input port. Among the different width variations calculation, the most relevant is based on a parametric function based on Lemniscate curves.
First nano- and microparticles of YIG were fabricated by using the Pulsed Laser Fragmentation in Liquids (PLFL) technique and characterized in solution. MO response was observed. Whereas the MO performance is not yet sufficient for the application, this first step has allowed us to identify possible paths for improvements. Attempts of MO sol-gel material deposition on metal and dielectric structures have started and show promising results for future insertion into slot waveguides.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

At this stage of the project, the results beyond the state of the art are related to the numerical design activities, which are leading to the definition of innovative configurations of magneto-optic integrated components. In particular, the electromagnetic analysis of the magneto-optic slot waveguide configuration has given insight into the magneto-biplasmonic effect, showing its dependence on the different parameters: the effect of the inclusion of an additional high-refractive index layer has been studied, showing an improvement of the isolation ratio. In addition, the designed slot waveguide of the 3-ports circulator has a variable width that allows the energy of the propagating modes to be transferred to one side of the slot within a minimum distance up to the output port: the optimum width variation calculation is based on a parametric function based on Lemniscate curves.
These results have been presented at international conferences.
Moreover, in preparation of transition sections design between dielectric input waveguides and MO slot waveguides, a model of MO coupled mode beating was established and submitted for publication.

Fig. 2 Slot waveguide proposed designs and propagation simulations in a 3-ports circulator

Fig. 1 Initial scheme and principle of the targeted circulator