ISO 1-on-1 LIDT test (21254-1,2)

1-on-1 test explained:

Use this test for:

• a feedback when optimizing polishing process and characterizing high defect densities;
• investigation of intrinsic material properties;
• screening experiments;
• reference, when quantifying “fatigue” or “conditioning” effects;

Test description

The entrance surface of an optical element is divided into a matrix of test sites. Each test site is then exposed to a single laser pulse using fixed laser irradiation level (peak fluence). Distinct irradiation levels are used for individual test sites. After exposure, the status of all test sites was inspected using offline microscopy. Collected damage statistics are interpreted to calculate damage probability versus applied laser irradiation level. Using this data set laser-induced damage threshold (LIDT) is calculated as the maximum applied laser irradiation level featuring zero damage probability. In the case of CW irradiation, the 1(Time)-on-1 test can be repeated using different pulse duration.

Known limitations and risks:

• 1-on-1 LIDT might be overestimated
  • when optical element features very low defect density, rare defects will be simply missed by small laser beam (use raster scan LIDT tests instead)
  • Ageing, fatigue or incubation effects are not considered;
• Annealing of neighboring test sites is possible at the CW regime;

Most popular test parameters for this test

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