A compact and robust method for spectropolarimetry

摘要

Motivated by astrobiological remote sensing needs, Sparks et al. (2012)~1 present an approach to spectropolarimetry which offers the prospect of high sensitivity over a very wide wavelength range (UV, optical, IR). Using static, robust components the polarization information is encoded onto one dimension of a two-dimensional data array, while the other dimension records the spectrum. A spatially varying retardance along the spectrograph slit, followed by a polarization analyzer, encodes the Stokes parameters as coefficients of orthogonal trigonometric functions perpendicular to the spectrum. No moving parts are required and all polarimetric information is available on a single data frame, hence the technique is immune to time dependencies, free of fragile modulating components, has the potential for high sensitivity while offering a wide wavelength range with full Stokes spectropolarimetry. Within the Solar System, spectropolarimetry offers diagnostics for dust (cometary, zodiacal, rings), surfaces (rocky, regolith, icy), aerosols (clouds, dust storms) and high energy plasma emission processes. Beyond the Solar System, space-based telescopic spectropolarimetry has important contributions to make in the detection of extrasolar planets and their characterization. There are astrobiological applications for full Stokes polarimetry stemming from the interaction of light with chiral living organisms, which offers the potential for a remote sensing detection capability for microbial life.