B-Pol Satellite experiment: HWP technologies comparison

1
B-Pol Satellite experiment HWP technologies
comparison
Giampaolo Pisano Radioastronomy Technology
Group Jodrell Bank Centre for Astrophysics,
University of Manchester, UK B-Pol Meeting -
Paris, 29-30 July 2010
2
Half-Wave Plates Requirements

• In sensitive multi-pixel array applications
  there are many demanding
• requirements for the HWP characteristics, lets
  mention the most general ones

3
Sapphire Achromatic HWPs Pancharatnam designs
G. Pisano et al., Applied Optics v45, n26
(2006) G. Savini et al., Applied Optics v45, n35
(2006)
- Recipes based on birefringent plates
(Ex 3-plates sapphire, no ARC)
10cm
4
G. Pisano et al., Applied Optics v45, n26
(2006) G. Savini et al., Applied Optics v45, n35
(2006)
Sapphire Achromatic HWPs Modelling FTS Tests
Results
Absorption calculation
Fast axis Transmission
Results
Extrapolated Minimum Cross Polarisation
Measured Cross-Polarisation
X-pol -25/-30dB
5
Sapphire Achromatic HWPs Quasi-Optical Tests
Co-Pol Cross-Pol Beams
- VNA measurements
Horn-OMT pixel HWP
Averaged Cross-Pol -29dB
(Across beam and frequency band)
6
Mesh Half-Wave Plate Air-gap design
G. Pisano et al., Applied Optics v47, n33 (2008)
Capacitive Stack
Inductive Stack
7
Mesh HWP Air-gap design results
G. Pisano et al., Applied Optics v47, n33 (2008)
Fast Axis Transmission
Slow Axis Transmission
Differential Phase-Shift
Cross-Polarisation
X-pol -25dB
8
Mesh HWP Dielectrically embedded design (v.1)
G. Pisano et al., to be submitted to Appl. Opt.
Capacitive Stack
Dj p
Inductive Stack
9
Mesh HWP Dielectrically embedded design (v.2)
G. Pisano et al., to be submitted to Appl. Opt.
20cm
Recipe with Inductive and Capacitive lines on the
same grid

• One C/L stack only
• ? Grids reduced by a factor 2
• Grids easier to align ? should have lower losses

10
Conclusions

• HWP studies
• Birefringent vs Mesh options
• We know how to model and build both
• Mesh HWP the most promising
• ? We should be able to meet all the requirements