Optomechanics and surface residues can be sources of contaminants when directly illuminated or subjected to laser scatter, which can then deposit and grow on optical surfaces leading to transmission loss over time. To extend the useful lifetime of laser systems and laser optic assemblies, it is necessary to determine best practices in material selection and handling of components both in and out of the beam path. We present lessons learned from a series of month-long (~100 trilllion shots) experiments performed at 355nm with laser parameters relevant to material processing and research (20ns pulsed ~1kW/cm^2 average). Laser-induced surface contamination and transmission losses of an assortment of optics in controlled and uncontrolled environments were monitored, and contamination mitigation techniques qualified by transmission measurement and microscopy.
There has been a concern with the typical Laser-Induced Damage Threshold (LIDT) testing due to the small allowable spot size and the small required tested area. With the current tests, it is possible to actually miss defects entirely, resulting in a higher LIDT value.
Experiments conducted in this study compare traditional LIDT measurements in the nanosecond regime made with a broad variant in spot sizes. These same spot sizes are also used to run larger area scans to evaluate the damage sites per area. Experimental results will be presented and discussed in the broader scope of developing a reliable LIDT standard.
Laser-induced contamination (LIC) can be a major concern of using UV laser systems. Surface contamination occurs via interactions between the UV laser and particulates, water vapor condensate, organics, and airborne molecular contaminates (AMC) from the environment or outgassing from system materials. A brief review of contamination of optics will lead into present results from long-term 355 nm quasi-CW laser transmission experiments at Edmund Optics. Time lapse microscopy was used to monitor nucleation and growth of surface contaminants. Laser burn boxes were constructed for use as a controlled UV LIC testbed; experimental results are presented on transmission losses for various material preparation methods.
Laser users desire optics that not only have a high laser induced damage threshold (LIDT), but also perform consistently over time. In fact, some aerospace and military applications can require long lifetime optics for remote environments where replacement is untenable. UV laser optics are susceptible to slow performance degradation with exposure to sub- Laser Induced Damage Threshold UV laser light due to the process of UV fatigue. Although UV fatigue of optics is well documented, the mechanisms are not well understood. Design and construction of a UV lifetime testbed to investigate the mechanisms of UV fatigue, preliminary results, and future directions are presented.
It is crucial in the laser optics industry to have reliable Laser Induced Damage Threshold(LIDT) testing to ensure quality optics that laser users can rely on, especially for high power or fluence laser experiments. In-house testing not only provides the QA/QC utility but also the necessary feedback loop to improve and develop quality laser optics. We present the development of a robust LIDT testbed at Edmund Optics with enough adjustability to accommodate testing according to the ISO Standards 21254 -1,-2,-3 and -4, in addition to applying new parameters and protocols for LIDT testing such as those being developed by the Optics and Electro-Optics Standards Council Task Force 7 (OEOSC-TF7). Difficulties in developing such a complex system(safety, automation, damage detection, etc.) will be presented as well as test results produced by the system to-date.
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