UV radiation effects on liquid crystal variable retarders for aerospace applications
Liquid-Crystal Variable Retarders (LCVRs)1 are optical devices that provide a variable optical retardance accomplished by the application of electric fields. Traditionally, they have been used as light polarization modulators for polarimetric applications in ground telescopes2, and more recently the...
| Main Authors: | , , , , , |
|---|---|
| Format: | Conference Object |
| Language: | English |
| Published: |
2012
|
| Subjects: | |
| Online Access: | https://orbi.uliege.be/handle/2268/131181 https://orbi.uliege.be/bitstream/2268/131181/1/UV%20radiation%20effects%20on%20Liquid%20Crystal%20Variable%20Retarders%20for%20aerospace%20applications.pdf |
| Summary: | Liquid-Crystal Variable Retarders (LCVRs)1 are optical devices that provide a variable optical retardance accomplished by the application of electric fields. Traditionally, they have been used as light polarization modulators for polarimetric applications in ground telescopes2, and more recently they took part in the polarisation modulation package of the Imaging Magnetograph eXperiment (IMaX)3, where the LCVRs were launched successfully on-board the Sunrise mission, a stratospheric balloon that was flown from Antarctica to study the solar magnetic fields. This mission was the precursor of the Solar Orbiter mission of the European Space Agency (ESA), where the liquid crystals will be used as polarisation modulators onboard a space mission for the first time in two instruments: the Polarimetric and Helioseismic Imager (SO/PHI) and the Multi-Element Telescope for Imaging and Spectroscopy (METIS). Any on-board element used for aerospace applications must be able to survive the harsh environmental space conditions including UV radiation, gamma radiation, vibrational tests, thermal-vacuum. In this sense, LCVRs have been recently validated to be used under the space conditions of the Solar Orbiter mission, in the framework of the ESA project: “Validation of LCVRs for the Solar Orbiter Polarisation Modulation Package”. In this project, a set of LCVRs with different design parameters has been analyzed under the different space environmental conditions. These design parameters include the architecture of the LCVR cell, using Anti-Parallel Aligned Nematic (APAN) and Hybrid Aligned Nematic (HAN) architectures, the type of liquid crystal molecules, using different commercial nematic liquid crystal mixtures with high and low birefringence and positive and negative dielectric anisotropy, different homogeneous and homeotropic polyimide alignment layers and different glass plates. Among the space environmental components, the UV radiation needs special consideration due to the organic nature of the liquid crystal molecules and ... |
|---|