Abstract
Micro-milling has been accepted as the most promising method to repair the micro-defects on the surface of KH2PO4 (KDP) optics. However, surface tool marks are inevitably introduced during the micro-milling repairing process, and could possess great potential risks in lowering the laser-induced damage threshold of KDP optics. The primary cause of laser damage growth of nonlinear crystals has been considered as its internal light intensification. In this work, how the tool marks impact the incident laser modulation as well as the laser-induced damage resistance of micro-milled KDP optics was theoretically and experimentally investigated. The results indicate that periodic tool marks can cause diffraction effect and result in significant relative light intensity modulation (IRmax), up to 5.6 times higher than that inside smooth crystal surfaces. Although the change trends of IRmax with respect to tool marks on both surfaces of KDP optics are similar, the IRmax induced by the rear-surface tool marks is nearly twice higher than that induced by the front-surface tool marks, which means the rear surface with tool marks are more vulnerable to be damaged. The period of tool marks determines the modulation degree and distribution patterns of light intensity inside KDP crystal while the residual height of tool marks can only slightly regulate the modulation degree of light intensity. The tool marks with a period of 1 μm normally give rise to serious light intensification and should be strictly excluded, while the period of tool marks from 10 μm to 20 μm is conducive to the laser damage resistance of micro-milled KDP optics, which were verified by the tests of transmittance capacity and laser damage resistance, and is supposed to be preferred in the actual repairing process of full-aperture KDP optics.
| Original language | English |
|---|---|
| Article number | 105610 |
| Journal | Optics and Laser Technology |
| Volume | 119 |
| DOIs | |
| Publication status | Published - 30 Nov 2019 |
Funding
This work is financially supported by the National Natural Science Foundation of China (No. 51775147, No. 51705105), Science Challenge Project (No. TZ2016006-0503-01), China Postdoctoral Science Foundation funded project (No. 2017M621260), Heilongjiang Postdoctoral Fund (No. LBH-Z17090) and Self-Planned Task (No. SKLRS201718A) of State Key Laboratory of Robotics and System (HIT). The first author also highly appreciates the support from China Scholarship Council. The authors declare that they have no competing interests. This work is financially supported by the National Natural Science Foundation of China (No. 51775147 , No. 51705105 ), Science Challenge Project (No. TZ2016006-0503-01 ), China Postdoctoral Science Foundation funded project (No. 2017M621260 ), Heilongjiang Postdoctoral Fund (No. LBH-Z17090 ) and Self-Planned Task (No. SKLRS201718A ) of State Key Laboratory of Robotics and System (HIT) . The first author also highly appreciates the support from China Scholarship Council.
| Funders | Funder number |
|---|---|
| Heilongjiang Postdoctoral Fund | |
| National Natural Science Foundation of China | 51705105, 51775147 |
| China Postdoctoral Science Foundation | 2017M621260 |
| China Scholarship Council | |
| State Key Laboratory of Robotics and System | |
| Science Challenge Project of China | TZ2016006-0503-01 |
Keywords
- KDP crystal
- Laser damage
- Light intensity modulation
- Micro ball-end milling
- Surface topography
- Tool marks
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering