Tunable dispersion compensation of quantum cascade laser frequency combs

Area of Science:

• Quantum optics
• Laser physics
• Mid-infrared photonics

Background:

• Achieving stable mid-infrared quantum cascade laser (QCL) frequency combs with broad spectral coverage presents a significant challenge.
• Group velocity dispersion (GVD) management is crucial for optimizing the performance and stability of these laser systems.

Purpose of the Study:

• To introduce and demonstrate a novel tunable dispersion compensation scheme for mid-infrared QCL frequency combs.
• To enhance the dynamic range of the comb regime and enable tuning of the optical comb's offset frequency.

Main Methods:

• Implementation of a tunable dispersion compensation scheme using a planar mirror placed behind the QCL's back facet.
• Utilizing a Gires-Tournois interferometer (GTI) configuration to precisely control and compensate for the laser's intrinsic dispersion.

Main Results:

• Demonstrated that the GTI can either enhance or decrease the dispersion, depending on mirror placement.
• Significantly increased the fraction of the comb regime within the laser's dynamic range by compensating for intrinsic dispersion.
• Achieved independent tuning of the optical comb's offset frequency using the GTI, with minimal impact on the repetition frequency.

Conclusions:

• The proposed tunable dispersion compensation scheme effectively addresses the challenge of GVD in mid-infrared QCL frequency combs.
• The GTI-based approach offers enhanced stability, broader spectral coverage, and independent control over key comb parameters, paving the way for advanced applications.