Quantum Cascade Lasers

Since I arrived at the Laboratoire Temps-Fréquence, I have been working on different possibilities to characterize and stabilize quantum cascade lasers (QCL). The lasers I have been using were developed by ETH Zurich, so these works are in collaboration with people from the Quantum Optoelectronics Group.

Control by illumination of the front facet

One major work to control frequency combs based on QCLs was to study a novel actuator based on a NIR light illuminating the front facet of the QCL-chip. A full characterization of this actuator has been made and we demonstrated a tight locking of a QCL-comb line on a DFB-QCL with a 10-fold improvement of the residual phase noise [APL-23]. This actuator was then used to design a master-follower dual-comb setup to study noise properties of stabilization schemes, which is difficult to perform in the MIR with other techniques [APR-24].

Figure: (Left) Phase noise PSD and (Right) RF spectrum of the beating between one QCL-comb line and a DFB-QCL depending on the stabilization method used. Adding the optical actuator results in nice improvements [APL-23].

We also demonstrated that the NIR light could be used for injection locking of the repetition frequency of a QCL-comb with enhanced performance compared to the usual electrical approach [APL-25]. For this, we modulated a NIR laser using a RF generator at a frequency close to the repetition frequency of the QCL, and we illuminated the front facet. Our results are in good agreement with Adler’s law of coupled oscillators.

Figure: Set of RF spectra obtained at the electrical extraction channel of a QCL-comb when sweeping the frequency of the generator (diagonal line) to observe the bandwidth Δf where the locking occurs [APL-25].

References

[APL-25] Alexandre Parriaux, Kenichi N. Komagata, Mathieu Bertrand, Mattias Beck, Valentin J. Wittwer, Jérôme Faist, and Thomas Südmeyer, “Non-resonant optical injection locking in quantum cascade laser frequency combs,” APL Photonics 10.6, 066113 (2025).
DOI: 10.1063/5.0253292

[APR-24] Alexandre Parriaux, Kenichi N. Komagata, Mathieu Bertrand, Valentin J. Wittwer, Jérôme Faist, and Thomas Südmeyer, “Dual-Comb Interferometry for Coherence Analysis of Tightly Locked Mid-Infrared Quantum Cascade Laser Frequency Combs,” Advanced Photonics Research 2024, 5, 2400006 (2024).
DOI: 10.1002/adpr.202400006

[APL-23] Kenichi N. Komagata, Alexandre Parriaux, Mathieu Bertrand, Johannes Hillbrand, Mattias Beck, Valentin J. Wittwer, Jérôme Faist, and Thomas Südmeyer, “Coherent control of mid-infrared frequency comb by optical injection of near-infrared light,” APL Photonics 8.8, 086110 (2023).
DOI: 10.1063/5.0156861