Design of a Multipurpose Photonic Chip Architecture for THz Dual-Comb Spectrometers

Area of Science:

• Photonics
• Integrated Optics
• Terahertz Technology

Background:

• Generating complex dual-comb (DC) terahertz (THz) signals typically requires electro-optic tunable systems.
• Existing methods lack scalability and cost-efficiency for widespread application.
• There is a need for integrated photonic solutions for versatile THz signal generation.

Purpose of the Study:

• To design and simulate a multipurpose photonic integrated circuit (PIC) for generating multiheterodyne complex DC THz signals.
• To translate electro-optic tunable DC system functionality onto a scalable and cost-efficient photonic chip.
• To enable general-purpose PICs for various THz applications.

Main Methods:

• An architecture based on a seed comb, mode selection, and a DC stage with a frequency shifter was designed.
• Optical Injection Locking (OIL) or Optical Phase-Locked Loops (OPLL) were evaluated for comb line selection.
• Double sideband suppressed carrier modulation and asymmetric Mach-Zehnder Interferometer filtering were used for frequency shifting.

Main Results:

• Simulations demonstrated a high-quality, frequency-shifted dual-comb signal with a side mode suppression ratio of 21 dB (41 dB after photodetection).
• A dual-comb with 10 kHz spacing and 5 Gbps OOK modulation was generated, down-convertible to THz range.
• The architecture proved multipurpose, suitable for THz communications and other applications.

Conclusions:

• The proposed PIC architecture offers a versatile, cost-efficient solution for complex DC THz signal generation.
• This work represents a significant step towards commercial THz photonic chips for spectroscopy, imaging, and telecommunications.
• The design's adaptability supports its fabrication via multi-project wafers, enhancing accessibility.