Microresonators for mid-IR laser analysis and control

High-Q crystalline Whispering Gallery Mode Resonators have proven to be powerful tools for characterization and stabilization of lasers from the UV to the MIR. Here, we report our recent results on Whispering Gallery Mode Resonators used for frequency characterization, stabilization and linewidth narrowing of Interband and Quantum Cascade Lasers. These results pave the way to new classes of compact MIR sources usable for Metrology, Fundamental Physics and Space missions. Our setup demonstrates the feasibility of a compact apparatus for sub-Doppler spectroscopy based on mid-IR laser sources stabilized on high-Q CaF2 Whispering Gallery Mode Resonators. Thanks to the high stability of the resonator, laser linewidth narrowing down to the 10-kHz level can be achieved. In addition, the very good stability on long timescales and the wide tunability makes this kind of sources suitable for high-precession molecular spectroscopy and metrological applications.