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Fluoride coatings for vacuum ultraviolet reflection filters
Applied Optics
|February 3, 2016
Summary
New LaF3/MgF2 reflection filters effectively discriminate atomic oxygen lines for vacuum ultraviolet imagers. These filters demonstrate high spectral resolution and can recover optical properties after environmental contamination using UV ozone cleaning.
Area of Science:
- Materials Science
- Optical Engineering
- Space Physics
Background:
- Atomic oxygen lines at 130.4 and 135.6 nm are crucial for remote sensing in Earth's upper atmosphere.
- Vacuum ultraviolet (VUV) imagers require filters with high spectral discrimination to isolate these specific wavelengths.
- Existing filter technologies may face challenges with spectral resolution and environmental stability.
Purpose of the Study:
- To develop and characterize LaF3/MgF2 reflection filters for enhanced spectral discrimination of atomic oxygen lines.
- To investigate the performance of these filters in VUV imagers.
- To assess the filters' environmental stability and methods for property recovery.
Main Methods:
- Preparation of LaF3/MgF2 multilayer filters using molybdenum-boat thermal evaporation.
- Optical property characterization using a high-precision VUV spectrophotometer.
- Evaluation of filter performance at different angles of incidence (7° and 45°).
- Testing environmental vulnerability and recovery using UV ozone cleaning.
Main Results:
- Optimized nonquarter-wave multilayer structures achieved high reflectance ratios (R135.6nm/R130.4nm) of 92.7 at 7° and 20.6 at 45°.
- Standard π-stack structures yielded a lower ratio of 12.4 at 7°.
- Demonstrated vulnerability of filter microstructures to environmental contamination.
- Showcased successful recovery of optical properties via UV ozone cleaning.
Conclusions:
- LaF3/MgF2 reflection filters offer high spectral-discrimination capacity for atomic oxygen lines.
- Optimized multilayer designs significantly enhance filter performance.
- The filters exhibit environmental sensitivity but can be restored using UV ozone cleaning, crucial for long-term VUV imager operation.
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