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854nm Beam2 (Arm3) has anomalously low modulation efficiency (35% vs 50%). 397nm Beam2 (Arm2) also has reduced efficiency. It is suspected that this is due to low polarization beam splitter contrast. Optical mitigation likely will be required, and modeling is ongoing. We note that subtraction of the intrinsic stray light (above) improved the modulation efficiency, but it remains at / below 38%.
Demodulation Sampling
Spatial scale for demodulation sampling is yet to-be-finalized. The initial “checkerboard” interpolation pattern, seen in earlier releases of ViSP data has now been fixed. However, several other issues create background signals. Further assessment is necessary to find the appropriate trade-off between errors and smoothness. The QUV continuum levels are at variable levels around 1%. We are currently investigating different observing techniques to also improve the polarization zero point performance.
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