4.8 μm difference-frequency generation using a waveguide-PPLN crystal and its application to mid-infrared Lamb-dip...

Area of Science:

• Laser physics
• Nonlinear optics
• Spectroscopy

Background:

• Mid-infrared light generation is crucial for various spectroscopic applications.
• Periodically poled lithium niobate (PPLN) waveguides offer a promising platform for nonlinear optical processes.

Purpose of the Study:

• To demonstrate difference-frequency generation (DFG) of 4.8 μm mid-infrared light using a PPLN waveguide.
• To evaluate the performance of the generated light source for high-resolution spectroscopy.

Main Methods:

• Difference-frequency generation was achieved using 871 nm and 1064 nm external-cavity diode lasers as pump sources.
• A periodically poled lithium niobate (PPLN) waveguide was employed for nonlinear frequency conversion.
• Lamb-dip spectroscopy of carbonyl sulfide was performed to assess the system's spectroscopic capabilities.

Main Results:

• A conversion efficiency of approximately 2%/W was achieved, producing 2 mW of output power.
• The generated mid-infrared light source demonstrated satisfactory performance for saturation spectroscopy.
• Lamb-dip spectroscopy revealed a laser linewidth of approximately 2 MHz, consistent with the pump lasers.

Conclusions:

• The PPLN waveguide DFG system is an effective source for generating 4.8 μm mid-infrared light.
• The system's performance is suitable for high-resolution saturation spectroscopy, as evidenced by carbonyl sulfide spectroscopy.
• The achieved laser linewidth indicates the potential for precise spectroscopic measurements.