Upconversion detector for range-resolved DIAL measurement of atmospheric CH₄

Area of Science:

• Atmospheric Science
• Optical Engineering
• Laser Technology

Background:

• Differential absorption lidar (DIAL) is crucial for atmospheric gas sensing.
• Accurate range-resolved detection of methane (CH4) is vital for environmental monitoring.
• Existing detectors can limit the performance of DIAL systems.

Purpose of the Study:

• To develop and demonstrate a robust, compact, portable, and efficient upconversion detector (UCD) for DIAL systems.
• To improve range-resolved methane (CH4) atmospheric sensing capabilities.
• To compare the performance of the UCD against conventional detectors.

Main Methods:

• The UCD utilizes an intracavity pump system.
• A 1064 nm pump laser is mixed with the 1646 nm lidar backscatter signal in a periodically poled lithium niobate crystal.
• The upconverted 646 nm signal is detected using a photomultiplier tube (PMT).

Main Results:

• The UCD demonstrated a noise equivalent power of approximately 127 fW/Hz^1/2.
• The UCD outperformed a conventional InGaAs avalanche photodetector in DIAL measurements.
• CH4 DIAL measurements achieved relative errors of less than 11% between 3 km and 9 km.

Conclusions:

• The developed UCD offers superior performance for DIAL-based methane sensing.
• This technology enables more accurate and efficient atmospheric methane detection.
• The UCD is a promising advancement for environmental monitoring applications.