Mid-infrared ethene detection using difference frequency generation in a quasi-phase-matched LiNbO3 waveguide.

Area of Science:

• Nonlinear optics
• Quantum electronics
• Spectroscopy

Background:

• Mid-infrared light sources are crucial for various applications, including trace gas detection.
• Periodically poled lithium niobate (PPLN) waveguides offer a promising platform for generating tunable mid-infrared radiation through nonlinear optical processes.

Purpose of the Study:

• To develop a tunable mid-infrared light source with high efficiency using a PPLN waveguide.
• To demonstrate the application of this source in sensitive trace gas detection.

Main Methods:

• Difference frequency generation (DFG) was employed by mixing two near-infrared diode lasers (1.064 µm and 1.583 µm) in a 48 mm long PPLN waveguide.
• Trace gas detection of ethene was performed using multipass absorption with wavelength modulation spectroscopy and cavity-enhanced absorption spectroscopy.

Main Results:

• The PPLN waveguide generated up to 200 µW of mid-infrared light tunable over ~35 cm⁻¹ around 3081 cm⁻¹.
• A high conversion efficiency of 12.3% W⁻¹ was achieved.
• Detection sensitivities of α(min)=8 x 10⁻⁹ cm⁻¹ Hz⁻¹/² (2σ) and 1.6 x 10⁻⁸ cm⁻¹ Hz⁻¹/² (2σ) were obtained for ethene.

Conclusions:

• The developed PPLN waveguide is an efficient source for tunable mid-infrared light generation.
• The system demonstrates excellent performance for trace gas detection, paving the way for sensitive environmental monitoring and industrial applications.