Presentations at Photonics West Conference Highlight Key Role the Technology Plays In Improving System Efficiency and Reducing Size and Costs​

CEA-Leti scientists presented three papers at Photonics West 2025 detailing the institute’s latest R&D successes to improve chemical detection, high-speed communication and LIDAR performance with integrated optics on silicon.

“Integrated optics on silicon will play an increasingly vital role in many diverse and critical applications, because photonic integrated components are compact, easy to manufacture and they allow integration of advanced materials,” said Cyril Fellous head of CEA-Leti’s Optics and Photonics Division.

The paper, “Design and Integration of Hybrid IIIV/Si Mid-Infrared Laser Sources and Photonic Circuits for Chemical Sensing Applications”, reports on the design, fabrication and characterisation of innovative hybrid III/V-on-silicon quantum-cascade lasers operating in the 4 µm-to-5 µm spectral range. This novel architecture increases the integration efficiency of these lasers compared to the monolithic ‘full-III/V’ approach.

“Because all passive functions of the lasers, such as optical feedback, waveguide routing, and power transfer, are defined into the silicon, more degrees of freedom are allowed for the design,” said Maxime Lepage, lead author of the paper. “Chemical sensing has become an active research area and a key application for mid-IR silicon-photonic devices due to their growing potential in spectroscopy, material processing, chemical and biomolecular sensing, security, and industrial applications,” Lepage explained.

The paper, “Design of Grating Coupler with Large and Flat Illumination Far-Field Profile for FMCW Flash LiDAR”, presents a grating coupler design that integrates key optical functions – beam separation and scene illumination – on a photonic chip. The grating coupler enables vertical light emission with a wide field of view (FOV) in both horizontal and vertical directions, maintaining a homogeneous far-field illumination profile.
This innovative design improves the optics of frequency modulation continuous wave (FMCW) flash LiDAR by integrating critical components into a single device, opening opportunities for compact and efficient LiDAR systems for applications such as autonomous driving, facial recognition and robotics.

“This integrated version of the illumination optics of an FMCW flash LIDAR is a first step towards an integrated version of this type of LIDAR,” explained the paper’s lead author, Paul Camus.

The paper, ‘Towards Fully Integrated Frequency Comb Based Transceivers’, reports advances in nonlinear photonics for high-speed communications on a silicon-nitride platform. The team fabricated ultralow-loss SiN waveguides and components on a 200mm wafer to generate a frequency comb and separate the comb lines. Such a circuit would reduce cost and consumption of high-speed transmitters by replacing many lasers with a single frequency comb source.
Optical frequency combs are a type of optical signal that contains many discreet and very stable wavelengths spaced regularly, thus acting as multiple parallel laser sources. They are generated using nonlinear optical processes in suitable materials, such as SiN.

“This achievement is an important step towards a fully integrated photonic transmitter based on nonlinear photonics,” said Baptiste Routier, lead author of the paper. “Those functions have been demonstrated separately, or if on the same chip, on different layers of materials. To our knowledge, it is the first time this has been achieved on the single layer, which is important because it simplifies the fabrication process and enhances overall device reliability.” ​