Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection

Area of Science:

• Optics and Photonics
• Spectroscopy
• Laser Physics

Background:

• Trace gas detection is crucial for environmental monitoring and industrial safety.
• Mid-infrared (mid-IR) laser sources offer high sensitivity for gas analysis due to strong molecular absorption lines.
• Developing compact, tunable, and narrow-linewidth mid-IR sources is an ongoing research area.

Purpose of the Study:

• To demonstrate a continuous-wave (cw) narrow-linewidth tunable mid-IR source for trace gas detection.
• To utilize difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal.
• To achieve high-resolution spectroscopy of ammonia (NH3).

Main Methods:

• A Ytterbium (Yb) fiber laser and a distributed feedback (DFB) laser diode were employed as pump sources for DFG.
• Difference frequency generation (DFG) was performed in a periodically poled LiNbO3 (PPLN) crystal.
• The DFB laser diode's current and temperature were varied to achieve frequency tuning.

Main Results:

• A tunable mid-IR source operating around 3 microns was successfully demonstrated.
• The source achieved an output power of approximately 2.5 microwatts (µW) with a spectral linewidth below 30 MHz.
• A frequency tuning range of 300 GHz (10 cm-1) was achieved.
• A high-resolution Doppler-broadened absorption spectrum of NH3 at 3295.4 cm-1 was obtained.
• A detection sensitivity of 24 parts per million-meter (ppm m) was estimated.

Conclusions:

• The developed Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source is effective for trace gas detection.
• The system demonstrates high-resolution spectroscopy capabilities, as evidenced by the NH3 spectrum.
• The achieved sensitivity indicates the potential for practical applications in gas sensing.