Mid infrared gas spectroscopy using efficient fiber laser driven photonic chip-based supercontinuum.

Area of Science:

• Optics and Photonics
• Spectroscopy
• Materials Science

Background:

• Supercontinuum generation in the mid-infrared (mid-IR) offers a robust method for accessing molecular functional group spectral regions.
• Silicon nitride (Si3N4) waveguides are promising for compact mid-IR frequency comb generation, but previous systems had limited spectral reach and efficiency.
• Accessing the 3-4 µm spectral region is crucial for many spectroscopic applications.

Purpose of the Study:

• To demonstrate efficient mid-IR supercontinuum generation in large cross-section Si3N4 waveguides.
• To achieve practical power levels and spectral coverage for spectroscopic applications.
• To showcase the potential for compact, chip-integrated spectroscopic and sensing devices.

Main Methods:

• Utilizing large cross-section silicon nitride waveguides.
• Pumping the waveguides with a 2 µm femtosecond fiber laser.
• Characterizing the generated supercontinuum spectrum and power conversion efficiency.
• Performing acetylene (C2H2) detection using absorption spectroscopy.

Main Results:

• Achieved supercontinuum generation in the 3-4 µm spectral region.
• Demonstrated up to 35% power conversion efficiency.
• Obtained milliwatt-level output powers.
• Successfully detected acetylene via absorption spectroscopy as a proof of principle.

Conclusions:

• Large cross-section Si3N4 waveguides pumped at 2 µm are effective for mid-IR supercontinuum generation.
• The developed source is suitable for compact, chip-integrated spectroscopic and sensing applications.
• This work advances the development of practical mid-IR frequency comb systems.