A polarimeter, to observe exoplanets in the visible and infrared, was built for the "Observatoire du Mont Mégantic" (OMM) to replace an existing instrument and reach 10 -6 precision, a factor 100 improvement. The optical and mechanical designs are presented, with techniques used to precisely align the optical components and rotation axes to achieve the targeted precision. A photo-elastic modulator (PEM) and a lock-in amplifier are used to measure the polarization. The typical signal is a high DC superimposed to a very faint sinusoidal oscillation. Custom electronics was developed to measure the AC and DC amplitudes, and characterization results are presented.
Nanocrystalline cellulose (NCC) solid films obtained from evaporated aqueous
heterogeneous mixtures retain the self-assembled chiral nematic order formed in
the suspension. These semi-translucent films are iridescent and reflect or
transmit circularly polarized visible light (400-700nm) due to the chiral
properties of the self-assembled nanostructure. This effect occurs at different
wavelengths depending on the pitch of the helical structure. In this paper, NCC
films have been fabricated from different recipes to produce various helix
pitches. The corresponding red-shift in the optical wavelength has been obtained
by means of Spectrophotometry measurements. Preliminary experiments have been
performed to investigate optical polarization effects as function of angles of
incidence using ellipsometry. Finally, laser micromachining results on NCC films
may suggest feasibility for integration as tunable light polarizer
components.
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