In situ non-perturbative temperature measurement in a Cs alkali laser

Area of Science:

• Laser Physics
• Optical Engineering
• Materials Science

Background:

• Diode Pumped Alkali Lasers (DPALs) are efficient sources of high-power laser light.
• Understanding temperature distribution in the gain medium is crucial for optimizing DPAL performance and longevity.
• Previous methods for temperature profiling were often perturbative or less precise.

Purpose of the Study:

• To experimentally determine the two-dimensional (2D) temperature profiles of the active-gain medium in a Cs + methane DPAL.
• To develop and validate a nonperturbative optical technique for in-situ temperature measurement.
• To quantify the thermal load and temperature rise within the DPAL gain medium under specific operating conditions.

Main Methods:

• Employed a Mach-Zehnder interferometer longitudinally coupled into the laser cavity.
• Probed optical path length distortions caused by refractive index changes due to heating in the gain medium.
• Analyzed interferograms using the QuickFringe software for accurate distortion measurement and subsequent temperature profile calculation.

Main Results:

• Successfully measured the 2D temperature profiles of the Cs + methane DPAL gain medium.
• Observed a maximum temperature rise of 58°C in the gain medium.
• Validated the nonperturbative interferometric technique for precise thermal mapping.

Conclusions:

• The developed Mach-Zehnder interferometry technique provides an accurate, nonperturbative method for measuring 2D temperature profiles in DPALs.
• The observed temperature rise highlights the importance of thermal management in Cs + methane DPAL systems.
• This technique can be applied to other laser systems for thermal characterization and optimization.