RESUMEN
We present a novel reflective quarter-wave plate comprised of subwavelength meanderline elements. The device is operational over the long-wave infrared (LWIR) spectrum, with significant spectral and angular bandwidths. Power reflection is approximately 70% over the majority of the LWIR. Efficient conversion from a 45° linear polarization state into circular polarization is demonstrated from finite-element electromagnetic simulations and from broadband polarimetric measurements.
RESUMEN
We compare three technological approaches for quarter-wave retarders within the context of polarimetric-imaging applications in the long-wave infrared (LWIR) spectrum. Performance of a commercial cadmium sulfide (CdS) crystalline waveplate, a multilayer meanderline structure, and a silicon (Si) form-birefringent retarder are evaluated under conditions of 8-12 µm broadband radiation emerging from an F/1 focusing objective. Metrics used for this comparison are the spectrally dependent axial ratio, retardance, and polarization-averaged power transmittance, which are averaged over the angular range of interest. These parameters correspond to the characteristics that would be observed at the focal-plane array (FPA) detector of an LWIR imaging polarimeter.
RESUMEN
A meanderline wave retarder is a unique type of frequency-selective-surface (FSS) that enables a change in the state of optical polarization. The principles of operation are very similar to a typical crystalline waveplate, such that the artificially structured meanderline array has both 'slow' and 'fast' axes that provide a phase offset between two orthogonal wave components. In this paper, we study the behavior and response of multilayered meanderline quarter-wave retarders designed for operation at 10.6 mum wavelength (28.28 THz). It will be shown that meanderline quarter-wave plates with more than a single layer exhibit improved transmission throughput at infrared frequencies due to impedance matching, similar to a multilayer optical film coating. Numerical data, both from simulations and measurements, are presented to validate this claim.