Closed-Loop Control of Visible Hybrid Photonic Systems

PhD Topic: Closed-Loop Control of Visible Hybrid Photonic Systems

The integration of visible laser sources with photonic integrated circuits is a key enabling technology for emerging applications in biophotonics, flow cytometry, spectroscopy, quantum sensing, and neural interfaces. Recent advances in flip-chip bonding and micro-transfer printing have demonstrated the feasibility of integrating visible laser diodes directly with complex silicon nitride photonic circuits, creating compact and scalable photonic systems. However, highly-integrated photonic systems remain sensitive to fabrication variations, packaging tolerances, temperature fluctuations, and long-term drift, often requiring extensive manual calibration.

To tackle this challenge, this PhD will focus on the development of self-monitoring and self-stabilizing hybrid photonic systems combining flip-chip integrated visible lasers and visible wavelength photonic circuits with monolithically integrated photodiodes and CMOS-based electrical control. The PhD candidate will be responsible for the photonics aspects of the research, including the design of integrated monitoring structures, laser-to-PIC interfaces, and demonstrator circuits, as well as their fabrication, assembly, and experimental characterization. In first instance, the PhD candidate will design test structures to demonstrate monolithically integrated closed loop optimization of the optical power, phase or wavelength of a single photonic element, e.g. an interferometer or ring resonator with thermo-optic phase shifter, or a hybrid integrated laser diode. In a later stage, larger photonic circuits with closed-loop control will be designed and tested, for example optical phased arrays for imaging applications [1], switching trees for optogenetics neural probes [2], photonic networks for programmable photonics [3] or neuromorphic photonic applications [4]. This work will build on existing imec expertise in heterogeneous laser integration and visible photonics, while extending these concepts towards actively controlled photonic systems.

The project will be carried out in close collaboration with a second researcher specializing in high-sensitivity analog and mixed-signal CMOS circuit design and closed-loop electronic feedback control. Together, both researchers will co-design photonic sensing structures and electronic control loops that enable automated control of the optical power, phase, wavelength, coupling efficiency, and photonic circuit performance. Success of the project will therefore rely on a strong interdisciplinary interaction between photonics design, packaging, and mixed-signal CMOS circuit design, requiring continuous exchange of models, requirements, measurements, and validation of data throughout the project.

The ultimate goal is to demonstrate a new class of intelligent hybrid photonic modules in which integrated lasers, photonic circuits, monitoring structures, and control electronics operate as a single closed-loop system. Such technology could significantly improve the robustness, scalability, and usability of future photonic systems and open up new opportunities in the fields of programmable photonics, microscopy, optical communications, quantum technologies, biomedical sensing, neuromorphic photonics and optical computing.

Keywords: Visible photonics, heterogeneous integration, flip-chip bonding, laser-PIC integration, photonic sensors, analog integrated circuits, feedback control, co-design, autonomous photonic systems, silicon nitride photonics.

[1] Filip Milojković, et al., Focusing through Scattering Media Using Integrated Photonics, ACS Photonics 16 (2024).

[2] X. Yang et al., A CMOS Neural Probe with 1280 Electrodes and 88 Emission Sites Featuring Thermo-Optic Switching and on-Chip Calibration for Dual-Wavelength Optogenetics, 2026 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, USA, 2026, pp. 616-618.

[3] Wim Bogaerts,  Programmable Photonics, Optics and Photonics News 35 (2024).

[4] Bhavin J. Sastri et al., Photonics for Artificial Intelligence and Neuropmorphic Computing, Nature Photonics 15 (2021).