Non-Degrading UV Mirrors
Fatigue effect – decrease of Laser-Induced Damage Threshold (LIDT) of optical materials after extended exposure to laser pulses. While catastrophic damage is more prominent, the real threat comes from the subtle but destructive fatigue effect-induced color change mode of LIDT. This effect severely degrades any optical element, leading to a decrease in the overall performance of the laser system or even downtime. Unfortunately, this critical issue tends to be underestimated or even ignored.
Imagine this scenario: A company decides to install standard market mirrors in its Ultrafast UV laser processing systems. After delivering the laser to the customer, it unexpectedly went into downtime after just 2,000 hours of use, causing costly downtime.
Upon investigation, the mirrors in the laser looked like the picture on the right, and the problem was diagnosed as color degradation of the standard mirrors.
In this fictional case, the laser manufacturer undergoes over €10,000 in laser repair costs – covering parts replacement, technician travel, and other expenses.
However, the laser manufacturer could have avoided this entire situation if they had used non-degrading UV optics from the start.
It’s easy to assume that having the highest possible LIDT guarantees the suitability of laser optics for an ultrafast high-power system. However, the UV part of the spectrum poses significant threats to laser optics, causing fatigue in the coating and leading to degradation and color change. This effect contributes to the fact that laser optics might become unusable after many pulses, although catastrophic damage was not reached.
The Solution
Acknowledging this problem and the fact that the aforementioned fictional case is common in the industry, OPTOMAN developed Ultrafast UV laser optics that can withstand over 10000 hours of laser irradiation, preventing downtime of the laser system. This achievement ensures that even after prolonged exposure to extreme Ultrafast UV light, the IBS-coated laser optics not only maintain the necessary parameters – consistent spectral performance and high Laser-Induced Damage Threshold (LIDT) — but are free of the color change effect. Moreover, this capability ensures better coating thermal conductivity.
The technology, which can be applied to Ultrafast HR and HR + HT coatings at 257-343 nm wavelengths for fs laser pulses, directly translates into lower maintenance costs, reduced downtime, longer overall lifespan, and consequently lower Total Cost of Ownership (TCO).
Lifetime extrapolation
Lifetime measurements were performed at Lidaris to prove the “non-degrading” statement. According to the measurements, OPTOMAN Ultrafast UV mirrors can withstand 0.35 J/cm² laser fluence with no color change after prolonged exposure to ultrafast laser irradiation.
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