An interferometric technique for transient phase shift measurements in an electron-beam-pumped laser

Area of Science:

• Plasma Physics
• Optical Metrology
• Laser-Induced Phenomena

Background:

• Electron-beam-pumped plasmas are crucial for various applications, but their optical homogeneity is challenging to measure.
• Existing techniques often require stringent environmental controls and lack spatial resolution.
• Accurate characterization of plasma optical properties is essential for understanding and optimizing these systems.

Purpose of the Study:

• To develop and characterize a novel interferometric technique for measuring optical homogeneity in electron-beam-pumped plasmas.
• To enable two-dimensional, transient phase shift contour mapping of excited plasma regions.
• To simplify the measurement process and reduce the need for extensive vibration isolation.

Main Methods:

• Utilizing a Mach-Zehnder interferometer coupled with a specialized electron-beam-pumped sample chamber.
• Implementing "e-beam partitioning" for single-shot absolute fringe shift measurements.
• Employing a short-pulse Xenon Fluoride (XeF) discharge laser for plasma excitation.
• Applying a ray calculus model for analyzing interferograms of graded index media.

Main Results:

• Demonstrated a two-dimensional transient phase shift contour mapping capability.
• Achieved absolute fringe shift measurements in a single shot, simplifying experimental setup.
• Presented sample interferograms for noble gas and noble gas-NF3 mixtures.
• Validated the applicability of a ray calculus model for interpreting the generated interferograms.

Conclusions:

• The developed interferometric technique effectively measures optical homogeneity in electron-beam-pumped plasmas.
• The system offers transient, 2D mapping with simplified experimental requirements.
• The ray calculus model provides a robust tool for analyzing plasma optical properties.