CEA-Leti presented new research at SPIE Photonics West detailing progress in integrating quantum cascade lasers (QCLs) with silicon photonic platforms for mid-infrared (MIR) applications.
The work, outlined in the paper “Advanced Architectures for Hybrid III-V/Silicon Quantum Cascade Lasers: Toward Integrated Mid-Infrared Photonic Platforms,” compares three distinct hybrid laser designs aimed at improving the practicality, flexibility, and scalability of MIR photonic systems.
Mid-infrared wavelengths are essential for applications including gas sensing, chemical spectroscopy, biomedical diagnostics, and security, due to strong molecular absorption features in this spectral region. However, existing MIR photonic systems are generally large, expensive, and challenging to manufacture at scale. Direct integration of MIR light sources onto silicon platforms is being pursued to achieve smaller, more robust, and more manufacturable devices, approaching the integration levels already common in near-infrared silicon photonics.
The three hybrid III-V/silicon QCL architectures presented are:
1. Hybrid Distributed Feedback QCL on Silicon-on-Nothing-on-Insulator with Adiabatic Coupling
This architecture delivers robust single-mode emission around 4.3 µm with efficient optical power transfer from the III-V active region into silicon waveguides. The high-index-contrast silicon photonics enable precise feedback and light routing, making the design suitable for scalable photonic integrated circuits intended for spectroscopy and chemical sensing applications.
2. Hybrid QCL with External Silicon Distributed Bragg Reflector Cavity
In this configuration, optical gain is provided by the III-V material while wavelength selection and optical feedback are implemented in a silicon-based distributed Bragg reflector (DBR) cavity. Separating gain and feedback functions increases design flexibility and supports development of tunable and multifunctional MIR sources for advanced spectroscopic and sensing systems.
3. Ultra-Compact QCL Micro-Sources Based on Photonic Crystals and Micro-Rings
These miniature sources achieve device footprints below 100 µm² by utilizing strong optical confinement and resonant effects, enabling high-density on-chip integration where size, power consumption, and integration density are critical requirements.
III-V/Si Photonic Crystal Surface Emitting QCL & Micro-resonator Ring
Credit: Alexis Holb
III-V/Si Distributed FeedBack QCL
Credit: Maxime LEPAGE
The presented results indicate that silicon photonics can take an active role in mid-infrared laser systems through approaches such as adiabatic optical coupling, silicon-based feedback mechanisms, and cavity engineering. Rather than proposing a single universal solution, the work offers multiple viable integration pathways that allow trade-offs between stability, design flexibility, and device footprint.
Alexis Hobl, the presenter and lead author of the paper, noted that combining quantum cascade lasers with silicon photonics moves mid-infrared sources closer to the integration density and manufacturing scalability already realized in near-infrared silicon platforms.
Future development efforts will concentrate on improving optical coupling efficiency, enhancing fabrication robustness, optimizing thermal and electrical management, and incorporating additional on-chip photonic functions such as filters, multiplexers, and interferometric circuits. Establishing wafer-scale reproducibility and packaging-compatible designs will represent important milestones toward fully integrated mid-infrared photonic systems.
The project received contributions from L’Institut des Nanotechnologies de Lyon (INL), III-V Lab, and Fraunhofer Applied Solid State Physics IAF.
