Quasi-phase-matched difference-frequency generation in periodically poled Ti:LiNbO(3) channel waveguides.

Area of Science:

• Photonics and Optics
• Nonlinear Optics
• Materials Science

Background:

• Mid-infrared (mid-IR) radiation is crucial for spectroscopy and sensing.
• Efficient generation of mid-IR light is challenging.
• Periodically poled lithium niobate (PPLN) waveguides offer a promising platform for nonlinear optical processes.

Purpose of the Study:

• To demonstrate efficient mid-infrared radiation generation via difference-frequency generation (DFG).
• To achieve a high normalized conversion efficiency in a PPLN channel waveguide.
• To explore the potential of integrated photonic devices for mid-IR applications.

Main Methods:

• Difference-frequency generation (DFG) was employed using pump radiation near 1.55 µm (tunable external-cavity laser) and signal radiation at 3.391 µm (HeNe laser).
• An 80-mm-long periodically poled Ti:LiNbO(3) channel waveguide was utilized as the nonlinear medium.
• The generated mid-IR radiation near 2.8 µm was measured.

Main Results:

• Mid-infrared radiation at approximately 2.8 µm was successfully generated.
• A normalized conversion efficiency of 105% W⁻¹ was achieved.
• This represents the highest reported normalized conversion efficiency for such a process to date.

Conclusions:

• Periodically poled Ti:LiNbO(3) channel waveguides are highly effective for efficient mid-IR generation via DFG.
• The achieved conversion efficiency highlights the potential for compact and powerful mid-IR sources.
• This work contributes to the advancement of integrated nonlinear optics for spectroscopic and sensing applications.