Mid-infrared phase modulators for free-space optical communications

• Applicant: Professor Mikhail Belkin, Ph.D.
• Subject Area: Communication Technology and Networks, High-Frequency Technology and Photonic Systems, Signal Processing and Machine Learning for Information Technology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568721130

Free-space optical communications in the mid-infrared transparency windows (4 − 5 μm and 8− 14 μm wavelength regions) is emerging as a viable solution for high bitrate data transmission. Driven by the high performances of quantum cascade lasers, unipolar quantum optoelectronics appears as the technology of choice for data transmission. Indeed, unipolar quantum devices are characterized by high-frequency response related to their short (~ps) excited state lifetime. Recently, free-space communication has been demonstrated by two members of this consortium (LPENS and Telecom) at 9µm wavelength with a record bitrate of 70 Gbits/s by using an amplitude modulator. A future major milestone for unipolar quantum optoelectronics is phase division multiplexing, enabled by phase modulators and stabilized coherent detection. Furthermore, integration of such devices in photonic integrated circuits will allow realizing compact systems for free-space optics. TUM has recently demonstrated that InP platform is very well suited for integration, as intrinsic InP and InGaAs lattice-matched on InP are transparent in the mid-infrared transparency window, as low background doping (below 10^15 cm^−3) can be achieved in these materials. The ambitious goal of doreMIPHASOL is to contribute to the field of free-space optics in the 4-5 µm transparency window by realising: a) A phase modulator integrated into a waveguide geometry to demonstrate a Mach-Zender interferometer; b) A detector integrated with a quantum cascade laser to create a heterodyne receiver. Data communication will be performed with these two systems. The consortium has the full span of skills necessary for the successful completion of the project.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partners: Professor Frédéric Grillot, Ph.D.; Professor Carlo Sirtori, Ph.D.