Raster scan LIDT test

Raster Scan Test explained:

Use this test for:

• To test samples with low-density (rare) defects;
• To measure damage density as a function of irradiation level (typically fluence or irradiance);
• To study conditioning, annealing, or laser cleaning effects;
• To study laser damage growth;
• To test/certify large optics;

Test description

During the sub-aperture raster scan test LIDT of the sample is investigated by performing covering large fraction of test sample. A selected area of the sample is scanned by moving laser beam with a spatial overlap between test sites. Spatial overlap is organized in such a way that at least 90% of peak fluence is applied always within entire test area. Surface is checked by microscope before and after scan. If no damage is detected scan is repeated over the same area with increased peak fluence. Starting from very low irradiation level values, it is linearly or non-linearly increased for every new scan until a damage event is detected or the maximum irradiation level of the system is reached. This test if continued above damage initiation threshold may also provide information about the damage density vs irradiation level. (See report example in Downloads section for details).

Known limitations and risks:

• No fatigue (incubation) effects are considered;
• Laser cleaning or conditioning is possible;
• Usually is time-consuming due to multiple microscopy after every scan;
• LIDT can be screened by contamination of surface by ablation products or poor handling;

Most popular test parameters for this test

⁽¹⁾ effective pulse duration measured at Full Width Half Maximum