Backward terahertz difference frequency generation via modal phase-matching in a planar LiNbO₃ waveguide

Area of Science:

• Nonlinear Optics
• Terahertz (THz) Photonics
• Waveguide Technology

Background:

• Terahertz (THz) radiation generation is crucial for various scientific and technological applications.
• Waveguide-based approaches offer enhanced control and efficiency for nonlinear optical processes.
• Modal phase-matching is a key technique for efficient nonlinear frequency conversion in integrated photonic devices.

Purpose of the Study:

• To investigate the generation of narrowband terahertz radiation using backward difference frequency generation (BDFG) in a SiO2-LiNbO3-air planar waveguide.
• To achieve modal phase-matching for efficient THz wave generation within the waveguide structure.
• To demonstrate the feasibility of BDFG for producing tunable, narrowband THz radiation.

Main Methods:

• Utilized a SiO2-LiNbO3-air planar waveguide structure.
• Employed the backward difference frequency generation process.
• Selected specific pump (TM0), signal (TE0), and idler (TE0 or TE2) modes to satisfy the phase-matching condition.

Main Results:

• Successfully generated narrowband terahertz radiation in the spectral range of 2.4-3.2 THz.
• Achieved a linewidth of less than 100 GHz for the generated THz radiation.
• Demonstrated modal phase-matching for BDFG in the specified waveguide configuration.

Conclusions:

• This study presents the first investigation of terahertz radiation generation in a waveguide via modal phase-matched backward difference frequency generation.
• The results highlight the potential of this waveguide-based approach for generating tunable, narrowband THz radiation.
• This work opens new avenues for integrated THz sources with potential applications in spectroscopy, imaging, and sensing.