Mid-infrared frequency comb for broadband high precision and sensitivity molecular spectroscopy

Area of Science:

• Optics and Photonics
• Spectroscopy
• Quantum Optics

Background:

• Frequency combs are precise optical rulers.
• Mid-infrared (mid-IR) light is crucial for molecular spectroscopy.
• Generating mid-IR combs from near-IR sources is challenging.

Purpose of the Study:

• To experimentally demonstrate the performance of a mid-IR frequency comb.
• To showcase its metrological and spectroscopic capabilities.
• To enable high-resolution spectroscopy of ambient air.

Main Methods:

• Nonlinear downconversion of a Ti:sapphire near-IR comb to generate a mid-IR comb.
• Phase-locking a quantum cascade laser (QCL) to the mid-IR comb.
• Measuring the frequency-noise power spectral density of the QCL.
• Direct comb spectroscopy of ambient air using the mid-IR comb and a Fabry-Perot cavity (Vernier technique).

Main Results:

• Successful generation of a mid-IR frequency comb.
• Phase-locking of a 4330 nm QCL to the mid-IR comb.
• Measurement of the QCL's frequency-noise power spectral density.
• Demonstration of ambient air spectroscopy with high resolution.

Conclusions:

• The mid-IR comb exhibits excellent metrological and spectroscopic performance.
• The developed system is suitable for high-precision molecular detection.
• This work advances coherent mid-IR light generation and application.