Metal-mesh achromatic half-wave plate for use at submillimeter wavelengths

University of Manchester, School of Physics and Astronomy, Manchester, UK.
Applied Optics (Impact Factor: 1.78). 12/2008; 47(33):6251-6. DOI: 10.1364/AO.47.006251
Source: PubMed


A metal-mesh achromatic half-wave plate (HWP) has been designed, manufactured, and tested for potential use in millimeter and submillimeter astronomical instruments. The prototype device presented here is based on a 12-grid Shatrow [IEEE Trans. Antennas Propag. 43, 109 (1995)] recipe to operate over the frequency range of 120-180 GHz. Transmission line modeling and finite-element analysis [Ansoft HFSS website:] were used to optimize the design geometrical parameters in terms of the device transmission, reflection, absorption, phase-shift, and cross-polarization as a function of frequency. The resulting prototype device was constructed and characterized using incoherent radiation from a polarizing Fourier transform spectrometer to explore its frequency and polarization behavior. These measurements are shown to be in excellent agreement with the models. Lists of the achieved HWP performance characteristics are reported.

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    • "Figure 5. First broadband mesh-HWP made with free standing metal mesh grids (figures from [10]). Figure 6. Examples of modelling and measurements of an air-gap mesh-HWP (plots from [10]). "
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    Proceedings of SPIE - The International Society for Optical Engineering 09/2014; 9153. DOI:10.1117/12.2056380 · 0.20 Impact Factor
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    • "This design uses capacitive and inductive metal-mesh geometries which each generate a frequency dependent phase shift with opposite sign. A first device fabricated from 6 capacitive grids and 6 inductive separated by air/vacuum gaps using accurately etched annular spacers demonstrated a bandwidth of 40 % (60 GHz) with a center frequency of 150 GHz [8]. Here we describe a procedure for optimizing the design of this type of HWP and present measurements of a device fabricated with a new process using dielectric spacers between the metallized sheets fused together with a hot pressing technique to make a solid self-supporting disc [9]. "
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    ABSTRACT: We describe a novel multilayered metal-mesh achromatic half-wave plate (HWP) for use in astronomical polarimetric instruments. The HWP is designed to operate across the frequency range from 125 to 250 GHz. The wave plate is manufactured from 12 layers of thin film metallic inductive and capacitive grids patterned onto polypropylene sheets, which are then bonded together using a hot-pressing technique. Transmission line modeling and three-dimensional electromagnetic simulations are used to optimize the parameters of the metal-mesh patterns and to evaluate their optical properties. A prototype HWP has been fabricated, and its performance is characterized in a polarizing Fourier transform spectrometer. The device performance is consistent with the modeling, although the measured differential phase shift for two orthogonal polarizations is lower than expected. This difference is likely to result from imperfect patterning of individual layers and misalignment of the grids during manufacture.
    Applied Optics 07/2011; 50(21):3750-7. DOI:10.1364/AO.50.003750 · 1.78 Impact Factor
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    • "Components fabricated using this technique have been used in a number of THz cameras and spectrometers [5] [6] [7] [8] [9]. More recently, the same technique has been used to manufacture half-wave plates using aligned metallic patterns with air-gap spacing between the layers [10]. These traditional metal mesh components are not considered metamaterials because their electromagnetic properties are not independent of their thickness, i.e. they cannot be characterized as having a bulk electric permittivity and magnetic permeability. "
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    ABSTRACT: We describe a novel artificial dielectric material which has applications at millimetre and submillimetre wavelengths. The material is manufactured from layers of metal mesh patterned onto thin polypropylene sheets which are then bonded together using a hot pressing process to provide planar rugged discs which can be reliably cycled to cryogenic temperatures. The refractive index of this material can be tuned by adjusting the geometry and spacing of the metal-mesh layers. We demonstrate its usage by designing and characterising a broadband anti-reflection coating for a Z-cut crystalline Quartz plate. The coating was fabricated and applied to the quartz using the hot press technique and characterized using a Fourier Transform Spectrometer. The performance is shown to be in good agreement with HFSS and transmission line modelling results.
    Applied Optics 07/2011; 48(35). DOI:10.1364/AO.48.006635 · 1.78 Impact Factor
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