Fully stabilized mid-infrared frequency comb for high-precision molecular spectroscopy.

Area of Science:

• Quantum Optics
• Spectroscopy
• Metrology

Background:

• Mid-infrared (MIR) optical frequency combs (OFCs) are crucial for high-precision measurements.
• Generating stabilized MIR OFCs is challenging, often requiring complex setups.
• Existing techniques struggle to access the 2.9–3.4 µm spectral range with high stability.

Purpose of the Study:

• To develop a fully stabilized MIR optical frequency comb.
• To demonstrate a simple and robust method for generating a MIR comb.
• To enable high-precision molecular spectroscopy and optical frequency metrology in the MIR.

Main Methods:

• Utilized half-harmonic generation within a femtosecond optical parametric oscillator (OPO).
• Transferred phase coherence from a stabilized near-infrared Er-doped fiber laser comb to the MIR.
• Employed a simplified approach requiring no phase-locked loops or additional reference lasers.

Main Results:

• Successfully generated a fully stabilized MIR OFC spanning 2.9–3.4 µm.
• Experimentally verified precise locking of MIR comb frequencies to the pump comb at sub-20 mHz level.
• Achieved a fractional statistical uncertainty of 2 × 10^-16 at the MIR comb's center frequency.

Conclusions:

• The developed MIR OFC is a powerful and simple tool for advanced scientific applications.
• This technique provides a highly accurate and stable frequency reference in the MIR region.
• The method overcomes limitations of previous stabilized frequency comb techniques in the MIR.