Generation of an optical frequency comb based on two cascaded dual-parallel polarization modulators

Area of Science:

• Photonics and Optical Engineering
• Applied Physics
• Electrical Engineering

Background:

• Optical frequency combs (OFCs) are crucial for precise frequency metrology and spectroscopy.
• Existing OFC generation methods using cascaded polarization modulators face limitations in spectral flatness and side-comb suppression ratio (SCSR).
• Low radio frequency (RF) drive voltage is desirable for practical OFC systems.

Purpose of the Study:

• To propose and investigate a novel OFC generation technique utilizing two cascaded dual-parallel polarization modulators (DPPolMs).
• To evaluate the performance of the proposed method in terms of spectral flatness, SCSR, and required RF drive voltage.
• To demonstrate the generation of OFCs with varying numbers of comb lines (25, 49, 81, 121).

Main Methods:

• Theoretical analysis and numerical simulations were employed to design and validate the proposed OFC generator.
• The study utilized theoretically obtained parameters for accurate simulation of the two-stage OFC generation process.
• Performance metrics including spectral flatness and SCSR were analyzed for different numbers of generated comb lines.

Main Results:

• The proposed two-stage DPPolM-based OFC generator demonstrated superior spectral flatness and SCSR compared to existing polarization modulator-based OFC generators.
• For a 49-line OFC, a power fluctuation of only 1 dB and an SCSR of 16.5 dB were achieved at a 3.5 GHz comb spacing.
• The method requires a significantly lower RF drive voltage than previously reported cascaded polarization modulator setups.

Conclusions:

• The novel two-stage DPPolM configuration offers a promising approach for generating high-performance optical frequency combs.
• This technique provides enhanced spectral quality and efficiency, making it suitable for advanced photonic applications.
• The demonstrated low RF drive voltage requirement enhances the practicality and potential for integration of this OFC generation method.