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The polarization process when polarizers act on an optical field is studied. We give examples for two kinds of polarizers. The first kind presents an anisotropic absorption - as in a polaroid film - and the second one is based on total reflection at the interface with a birefringent medium. Using the Stokes vector representation, we determine explicitly the trajectories of the wave light polarization during the polarization process. We find that such trajectories are not always geodesics of the Poincare sphere as it is usually thought. Using the analogy between light polarization and special relativity, we find that the action of successive polarizers on the light wave polarization is equivalent to the action of a single resulting polarizer followed by a rotation achieved for example by a device with optical activity. We find a composition law for polarizers similar to the composition law for noncollinear velocities in special relativity. We define an angle equivalent to the relativistic Wigner angle which can be used to quantify the quality of two composed polarizers.
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An ultra-broadband transverse magnetic (TM) pass hyperuniform disordered photonic crystal (HUDPC) polarizer is proposed and demonstrated on a silicon-on-insulator platform. Propagation of the transverse electric mode is blocked by three combined effects, including the photonic bandgap (PBG) effect, diffusive (non-resonant) scattering, and bandedge resonances. Specially, the designed 30-dB bandwidth in polarization extinction ratio (PER) of 265 nm is much larger than the spectral width of the PBG (149 nm) due to using the bandedge resonances. The TM mode is in the subwavelength regime of the HUDPC and thus has a low insertion loss (IL). An ultrawide 30-dB bandwidth in PER of 210 nm (1.44-1.65 um) is experimentally demonstrated in a 12.9-um-long HUDPC polarizer with spectrally averaged PER of 39.6 dB and IL for the TM mode of 1.1 dB (IL = 0.6 dB at 1.55 um). The HUDPC polarizers can be an excellent candidate for ultra-broadband polarization filtering in the silicon photonic platform.
We report single and multiband linear polarizers for terahertz (THz) frequencies using cut-wire metamaterials (MM). The MMs are designed by finite element method, fabricated by electron beam lithography, and characterized by THz time-domain spectroscopy. The MM unit cells consist of single or multiple length cut-wire pads of gold on semi-insulating Gallium Arsenide for single or multiple band polarizers. The dependence of the resonance frequency of the single band polarizer on the length of the cut-wires is explained based a transmission line model.
We have investigated the use of inkjet printing technology for the production of THz range wire-grid polarizers using time-domain terahertz spectroscopy (TDTS). Such technology affords an inexpensive and reproducible way of quickly manufacturing THz range metamaterial structures. As a proof-of-concept demonstration, numerous thin silver-nanoparticle ink lines were printed using a Dimatix DMP-2831 printer. We investigated the optimal printing geometry of the polarizers by examining a number of samples with printed wires of varying thickness and spacing. We also investigated the polarization properties of multiply-stacked polarizers.
The control of polarization, an essential property of light, is of wide scientific and technological interest. Polarizer is an indispensable optical element for direct polarization generations. Except common linear and circular polarizations, however, arbitrary polarization generation heavily resorts to bulky optical components by cascading linear polarizers and waveplates. Here, we present a general strategy for designing all-in-one full Poincare sphere polarizers based on perfect arbitrary polarization conversion dichroism, and realize it in a monolayer all-dielectric metasurface. It allows preferential transmission and conversion of one polarization state locating at an arbitrary position of the Poincare sphere to its handedness-flipped state, while completely blocking its orthogonal state. In contrast to previous work with limited flexibility to only linear or circular polarizations, our method manifests perfect dichroism close to 100% in theory and exceeding 90% in experiments for arbitrary polarization states. Leveraging this tantalizing dichroism, our demonstration of monolithic full Poincare sphere polarization generators directly from unpolarized light can enormously extend the scope of meta-optics and dramatically push the state-of-the-art nanophotonic devices.
We report the largest broadband terahertz (THz) polarizer based on a flexible ultra-transparent cyclic olefin copolymer (COC). The COC polarizers were fabricated by nanoimprint soft lithography with the lowest reported pitch of 2 or 3 micrometers and depth of 3 micrometers and sub-wavelength Au bilayer wire grid. Fourier Transform Infrared spectroscopy in a large range of 0.9 -20 THz shows transmittance of bulk materials such as doped and undoped Si and polymers. COC polarizers present more than doubled transmission intensity and larger transmitting band when compared to Si. COC polarizers present superior performance when compared to Si polarizers, with extinctions ratios of at least 4.4 dB higher and registered performance supported by numerical simulations. Fabricated Si and COC polarizers show larger operation gap when compared to a commercial polarizer. Fabrication of these polarizers can be easily up-scaled which certainly meets functional requirements for many THz devices and applications, such as high transparency, lower cost fabrication and flexible material.
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