1 MHz-resolution dual electro-optic frequency comb spectroscopy via multi-frequency small-signal modulation

Area of Science:

• Photonics and Optical Engineering
• Spectroscopy
• Quantum Optics

Background:

• Electro-optic frequency combs (EOFCs) are crucial for high-resolution spectroscopy.
• Existing methods face challenges in achieving high flatness and suppressing unwanted spectral components.
• The need for improved EOFC generation techniques is driven by advanced applications in sensing and metrology.

Purpose of the Study:

• To introduce a new EOFC generation method using multi-frequency small-signal modulation.
• To demonstrate the generation of high-resolution and high-flatness EOFCs.
• To validate the applicability of the generated EOFCs in dual-comb spectroscopy and stimulated Brillouin scattering measurements.

Main Methods:

• Utilizing a single-driver Mach-Zehnder modulator (MZM) biased at its minimum-transmission point.
• Implementing multi-frequency small-signal modulation to suppress optical carrier and even-order sidebands.
• Generating EOFCs with repetition rates of 1 MHz and 1.000025 MHz, featuring approximately 8000 comb lines with <1 dB flatness over a 40 MHz span.

Main Results:

• Successfully generated two distinct EOFCs with high line counts and flatness.
• Applied the generated EOFCs to measure molecular absorption of H¹³C¹⁴N near the P(10) rotational transition.
• Demonstrated the EOFCs' capability for high-resolution spectral characterization through stimulated Brillouin scattering (SBS) measurements in optical fiber.

Conclusions:

• The proposed EOFC generation scheme is effective and versatile for precision spectroscopic applications.
• The method offers a significant advancement in generating high-quality frequency combs.
• This technique opens new avenues for high-resolution spectral analysis and metrology.