1.645 µm Er:YAG single-mode dual-wavelength emitter for CH₄ differential absorption lidar

Area of Science:

• Laser Physics and Photonics
• Atmospheric Science and Remote Sensing
• Spectroscopy

Background:

• Differential absorption lidar (DIAL) requires precise dual-wavelength laser sources for atmospheric gas monitoring.
• Methane (CH4) detection is critical for climate change studies and environmental monitoring.
• Existing laser sources may face challenges in achieving stable, equal-energy output at specific absorption lines.

Purpose of the Study:

• To develop and characterize a novel hybrid fiber/bulk laser source operating at 1.645 µm for methane (CH4) monitoring via DIAL.
• To evaluate the laser's suitability for coherent wind Doppler lidar applications.
• To demonstrate stable, equal-energy dual-wavelength pulse generation for DIAL measurements.

Main Methods:

• Utilized a Q-switched Er:YAG ring cavity laser system.
• Pumped the cavity using erbium fiber lasers operating at 1532 nm.
• Sequentially seeded the laser with two fiber-coupled continuous-wave distributed feedback (DFB) laser diodes at CH4 absorption (ON) and non-absorption (OFF) wavelengths (1645.55 nm and 1645.30 nm).

Main Results:

• Achieved dual-wavelength laser operation at 1.645 µm with equal pulse energies (9 mJ) and durations (300 ns) at a 1 kHz repetition rate.
• Demonstrated stable spectral properties and high spectral purity in the dual-wavelength regime, despite gain differences in the gain medium.
• Confirmed the laser's capability for differential absorption lidar (DIAL) measurements.

Conclusions:

• The developed hybrid fiber/bulk laser source is highly effective for atmospheric methane (CH4) monitoring using DIAL.
• The system's ability to produce equal-energy pulses at specific wavelengths is crucial for accurate lidar measurements.
• The laser source shows promise for advanced atmospheric sensing applications, including wind Doppler lidar.