Dual-comb spectroscopy with a phase-modulated probe comb for sub-MHz spectral sampling

Area of Science:

• Optics and Photonics
• Spectroscopy
• Quantum Optics

Background:

• Frequency combs are precise light sources with evenly spaced spectral lines.
• Reducing mode spacing (densification) is crucial for high-resolution spectroscopy.
• Existing densification methods have limitations in simplicity or power conservation.

Purpose of the Study:

• To present a novel, efficient method for frequency comb mode spacing reduction.
• To demonstrate the application of the densified comb in high-resolution dual-comb spectroscopy.
• To highlight the advantages of the proposed binary phase modulation technique.

Main Methods:

• Implementing binary pseudo-random phase modulation on a frequency comb's pulse train.
• Utilizing the densified frequency comb for dual-comb spectroscopy.
• Performing spectroscopic measurements on a long-delay Mach-Zehnder interferometer and a microresonator.

Main Results:

• Successfully reduced the mode spacing of the frequency comb.
• Achieved sub-MHz spectral sampling in dual-comb spectroscopy.
• Demonstrated the effectiveness of the method on optical components.

Conclusions:

• Binary pseudo-random phase modulation offers a simple and efficient way to densify frequency combs.
• The technique preserves the initial comb power and combines advantages of other methods.
• This approach facilitates high-resolution spectroscopic measurements with enhanced spectral sampling.