Quasi-continuous burst-mode laser for high-speed planar imaging

Area of Science:

• Laser Physics and Engineering
• Combustion Science and Diagnostics
• Optical Engineering

Background:

• Traditional flashlamp-pumped Nd:YAG lasers have limitations in pulse-burst duration for advanced combustion studies.
• Extended pulse durations are crucial for capturing transient phenomena in fluid-flame interactions.
• High-repetition-rate laser systems are needed for time-resolved imaging of dynamic combustion processes.

Purpose of the Study:

• To extend the pulse-burst duration of a compact burst-mode Nd:YAG laser system.
• To evaluate the performance of the enhanced laser for high-speed, time-resolved flame diagnostics.
• To investigate unsteady fluid-flame interactions using advanced laser-induced fluorescence imaging.

Main Methods:

• Incorporation of a fiber oscillator and diode-pumped solid-state amplifiers to extend pulse-burst duration.
• Characterization of the laser system, including linewidth (<2 GHz at 1064.3 nm) and pulse energy (150 mJ at 10 kHz).
• Application of the third-harmonic output (354.8 nm) for planar laser-induced fluorescence (PLIF) of formaldehyde in a methane-air diffusion flame.

Main Results:

• Achieved an order-of-magnitude extension in pulse-burst duration compared to previous designs.
• Successfully acquired 100 and 200 sequential images of unsteady fluid-flame interactions at 10 kHz and 20 kHz, respectively.
• Demonstrated the capability of the enhanced laser system for high-speed, time-resolved combustion imaging.

Conclusions:

• The developed fiber oscillator and diode-pumped amplifier system significantly enhances Nd:YAG laser performance for combustion research.
• The system enables high-repetition-rate, time-resolved imaging of complex flame dynamics.
• This advancement provides a powerful tool for detailed investigation of unsteady fluid-flame interactions.