Fabrication of pixelated polarizer array and its application in polarization enhancement

Abstract

Pixelated polarizer array can be used in the real-time measurement of Stokes parameters. In this paper, pixelated polarizer array based on the aluminum nano-grating is designed and fabricated, and the fabrication technology is electron beam exposure technology. The size of each unit is 7.4 μm, and the polarization directions of each adjacent 2×2 units in the polarizer array are 0, π/4, π/2, and 3π/4. The period, duty cycle, depth and surface type of the grating are 140 nm, 0.5, 100 nm and rectangle type, respectively. The scanning electron micrographs of the pixelated polarizer array show that there is no disconnection, cross and pollution on the fabricated metal nano-grating lines. The nano-grating lines are straight and uniform in thickness, and the surface type of the grating is ideal rectangular type. The polarization optical micrographs show that the pixelated polarizer array has good polarization characteristics. The maximum polarization transmissivity can reach 79.3%, and the extinction ratio can arrive at 454. Furthermore, the pixelated polarizer array is integrated with the charge coupled devise chip, and the Stokes parameters can be calculated from one frame, then the degree of linear polarization and angle of linear polarization can be obtained. Thus, the polarization enhancement of image is achieved, which can be used in the anti-stealth and recognition.

Error analysis and optimal design of polarization calibration unit for solar telescope *

“…It is known from Eq. ( 6) that FOV effect induces the FOV-dependent distribution of ∆𝑀 wp (3, 3), ∆𝑀 wp (3,4), ∆𝑀 wp (4, 3), and ∆𝑀 wp (4, 4) as shown in Fig. 7.…”

“…Retardation error comes from the thickness error of a waveplate in manufacture, and it leads to the retardation of quarter waveplate deviating from the π/2, and will induce the crosstalk between linear polarization and circular polarization. Mueller matrix error ∆𝑀 wp of quarter waveplate can be calculated from ∆𝑀 wp = |𝑀 wp − 𝑀 QWP |, where only ∆𝑀 wp (3, 3), ∆𝑀 wp (3,4), ∆𝑀 wp(4,3) , and ∆𝑀 wp (4,4) are not zero, and also, ∆𝑀 wp (3, 3) = ∆𝑀 wp (4, 4), and ∆𝑀 wp (3, 4) = ∆𝑀 wp (4, 3). Figure 3 exhibits the relationship between ∆𝑀 wp (3, 3) and ∆𝑀 wp (3,4) and retardation error ∆δ = δ − π/2, and it is required that retardation error is less than 0.001 rad if crosstalk is less than 10 −3 among I, Q, U, and V .…”

“…Mueller matrix error ∆𝑀 wp of quarter waveplate can be calculated from ∆𝑀 wp = |𝑀 wp − 𝑀 QWP |, where only ∆𝑀 wp (3, 3), ∆𝑀 wp (3,4), ∆𝑀 wp(4,3) , and ∆𝑀 wp (4,4) are not zero, and also, ∆𝑀 wp (3, 3) = ∆𝑀 wp (4, 4), and ∆𝑀 wp (3, 4) = ∆𝑀 wp (4, 3). Figure 3 exhibits the relationship between ∆𝑀 wp (3, 3) and ∆𝑀 wp (3,4) and retardation error ∆δ = δ − π/2, and it is required that retardation error is less than 0.001 rad if crosstalk is less than 10 −3 among I, Q, U, and V .…”

“…At present, the solar magnetic field is mainly measured by polarization technique based on Zeeman effect theory and the polarized radiation transfer model of the solar atmosphere, [1,2] especially in the visible and near infrared wavelength region. Therefore, polarization measurement [3,4] is the core technology of the solar telescope. Now the next-generation large-aperture solar telescopes are expected to achieve extremely high polarization measurement accuracy.…”

A bio-inspired model for bidirectional polarisation detection

“…Based on Stokes theory [5], pixilated polarization filters are used at given orientations to maximize signal to noise ratio imaging of polarization information. The system of polarimeters includes a 2 × 2 pixels array and four micro-polarisers with different polarisation directions for an image point.…”