2-μm Ho emitter-based coherent DIAL for CO(2) profiling in the atmosphere

Area of Science:

• Atmospheric Science
• Optical Remote Sensing
• Spectroscopy

Background:

• Accurate atmospheric carbon dioxide (CO(2)) monitoring is crucial for climate studies.
• Traditional methods often lack the required spatiotemporal resolution for detailed atmospheric analysis.
• Advancements in laser technology offer potential for improved lidar-based measurements.

Purpose of the Study:

• To demonstrate the efficacy of a thulium-fiber-pumped holmium-based emitter in a Coherent Differential Absorption Lidar (CDIAL) system.
• To achieve high time and space resolution for atmospheric CO(2) absorption measurements.
• To validate the CDIAL system's performance against in situ measurements.

Main Methods:

• Utilized a 2-μm high-power dual-wavelength single-mode Q-switched Ho:YLF oscillator for CDIAL.
• Employed short pulse duration (40 ns) and high repetition rate (2 kHz) for enhanced precision.
• Conducted a 20-hour experiment comparing CDIAL CO(2) estimates with in situ gas analyzer data.

Main Results:

• The CDIAL system achieved 150-m range and 15-min time-resolved CO(2) absorption coefficients.
• Calculated instrumental error was 0.5% at 500 m and less than 2% at 1 km.
• Demonstrated good agreement between CDIAL-derived and in situ measured dry-air CO(2) mixing ratios.

Conclusions:

• The thulium-fiber-pumped holmium-based emitter is effective for high-resolution atmospheric CO(2) monitoring.
• The CDIAL system offers a precise and reliable method for measuring CO(2) absorption.
• This technology advances the capability for detailed atmospheric composition analysis.