Behind the Scenes of Eye-Safe Laser Rod Manufacturing for Defense LRF Applications
Hello everyone, my name is Avi Schiff, Technical Director at Arsuf Lasers.
In the video accompanying this post, I share real-world experience we gained while manufacturing laser rods for defense laser range-finding (LRF) applications, with a focus on eye-safe operation at 1.54 µm.
Why Erbium Glass?
For eye-safe LRF systems, erbium-doped glass (Er:Glass) is often the most suitable gain medium. However, phosphate-based erbium glass is highly sensitive to heat and air exposure, which directly impacts coating integrity and laser-induced damage threshold (LIDT).
The Challenge
One particularly demanding project required us to manufacture 1 mm diameter Er:Glass rods meeting a laser damage specification exceeding 25 J/cm².
At that time, our customer was suffering from frequent and costly coating failures, intermittently shutting down their production line. Traditional coating routes – despite involving reputable coating houses – were unable to achieve the required LIDT.
Rethinking the Fabrication Process
The conventional method involved:
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Grinding rods to the final diameter
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Stacking them in sacrificial resin fixtures
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Polishing and coating in batch form
While common, this process introduced subsurface damage and contamination, ultimately degrading coating performance.
We therefore adopted a non-traditional approach:
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Polish and coat the bulk material first
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Core the rods afterward using precision coring tools
Although promising, early yields were still insufficient.
Root-Cause Analysis & Process Innovation
Our conclusion was clear:
We had to deeply investigate the interaction between erbium glass material properties and fabrication methods.
By:
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Analyzing failure mechanisms
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Identifying stress, contamination, and thermal contributors
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Designing dedicated tooling and process controls
we established a robust manufacturing flow.
The result:
Thousands of 1 mm Er:Glass rods produced with negligible rejection rates, fully meeting demanding LIDT and reliability requirements.
A Hidden Specification: Lifetime
I’ll close with an often-overlooked parameter – life expectancy.
In the final image shown, you can see coating degradation only after several million laser shots, demonstrating long-term operational robustness, not just initial LIDT compliance.
If you are facing coating damage issues, yield limitations, or lifetime concerns in Er:Glass or other laser rod materials, we welcome you to consult with us.
